Obgyn Topic 1-8 Flashcards
(319 cards)
1
Q
- What are the bones that form the bony pelvis?
A
The bony pelvis consists of the paired innominate bones (ilium, ischium, and pubis), sacrum, and coccyx.
2
Q
Where are the innominate bones joined anteriorly and posteriorly?
A
The innominate bones are joined anteriorly at the symphysis pubis and posteriorly articulate with the sacrum at the sacroiliac joints.
3
Q
What happens to the joints of the bony pelvis during pregnancy?
A
During pregnancy, the joints relax to allow some mobility during labor and birth.
4
Q
How is the bony pelvis divided?
A
The bony pelvis is divided into the false pelvis and the true pelvis by the pelvic brim.
5
Q
What are the sections of the true pelvis?
A
The true pelvis is divided into three sections: the pelvic inlet, mid-pelvis, and pelvic outlet.
6
Q
What are the boundaries of the pelvic inlet?
A
The pelvic inlet is bounded anteriorly by the superior surface of the pubic bones and posteriorly by the promontory and alae of the sacrum.
7
Q
What is the mid-pelvis level?
A
The mid-pelvis is at the level of the ischial spines.
8
Q
What are the boundaries of the pelvic outlet?
A
The pelvic outlet is bounded anteriorly by the lower border of the symphysis, laterally by the ischial tuberosities, and posteriorly by the tip of the sacrum.
9
Q
What does the term vulva refer to?
A
Vulva refers to the female external genitalia, including the mons pubis, labia majora, labia minora, clitoris, external urinary meatus, vestibule of the vagina, vaginal orifice, and hymen.
10
Q
What is the mons pubis composed of?
A
The mons pubis is composed of a fibrofatty pad of tissue above the pubic symphysis and is covered with dense pubic hair.
11
Q
What are the labia majora?
A
The labia majora are two longitudinal cutaneous folds extending from the mons pubis to the perineum, with an outer hair-covered surface and an inner smooth layer.
12
Q
What do the labia majora enclose?
A
The labia majora enclose the pudendal cleft, into which the urethra and vagina open.
13
Q
What are the labia minora?
A
The labia minora are enclosed by the labia majora and divide anteriorly to enclose the clitoris, forming the prepuce and frenulum.
14
Q
Where is the clitoris located and what is its structure?
A
The clitoris is situated between the anterior ends of the labia minora and consists of two corpora cavernosa of erectile tissue enclosed in a fibrous sheath.
15
Q
What is the role of the clitoris in sexual function?
A
The clitoris plays an important role in sexual stimulation due to its rich supply of sensory nerve endings.
16
Q
What is the vestibule in the female genitalia?
A
The vestibule is a shallow depression between the labia minora, with the external urethral orifice opening anteriorly and the vaginal orifice posteriorly.
17
Q
Where do Bartholin’s glands drain?
A
Bartholin’s glands drain into the vestibule at the posterior margin.
18
Q
What are Skene’s ducts?
A
Skene’s ducts lie alongside the lower 1cm of the urethra and drain into the vestibule.
19
Q
Where is the external urethral orifice located?
A
The external urethral orifice lies 1.5–2 cm below the base of the clitoris and is covered by the labia minora.
20
Q
What is the hymen and what happens after it is penetrated?
A
The hymen is a thin fold of skin covering the vaginal orifice. After penetration, its remnants form the carunculae myrtiformes, nodules of fibrocutaneous material.
21
Q
Where are Bartholin’s glands located, and what is their function?
A
Bartholin’s glands are located on either side of the vaginal introitus, and they secrete mucus during sexual arousal.
22
Q
What causes Bartholin’s cysts?
A
Bartholin’s cysts form due to the occlusion of the gland duct, leading to fluid accumulation in the duct.
23
Q
What is the vagina and its length in a mature female?
A
The vagina is a muscular tube about 6-7.5 cm long in the mature female, lined by non-cornified squamous epithelium.
24
Q
How does the vagina adapt during parturition?
A
The vagina is capable of considerable distension to accommodate the passage of the fetal head during parturition.
25
Where is the vagina located in relation to the anal canal, rectum, and peritoneum?
The vagina is separated from the anal canal by the perineal body, lies in apposition to the ampulla of the rectum in the middle third, and is covered by the peritoneum of the rectovaginal pouch in the upper segment.
26
What is the vaginal vault and what are its zones?
The vaginal vault is where the uterine cervix protrudes into the vagina, with four zones: the anterior fornix, posterior fornix, and two lateral fornices.
27
What is the pH of the vagina in a sexually mature, non-pregnant female and its function?
The pH of the vagina is between 4.0 and 5.0, which has an antibacterial function, reducing the risk of pelvic infection.
28
What are the functions of the vagina?
The functions of the vagina are copulation, parturition, and the drainage of menstrual loss.
29
What is the uterus, and where is it located?
The uterus is a hollow, muscular, pear-shaped organ situated in the pelvic cavity between the bladder anteriorly and the rectum and pouch of Douglas posteriorly.
30
What are the dimensions of the uterus in a sexually mature female?
The uterus is approximately 7.5 cm long and 5 cm wide in a sexually mature female.
31
What is the normal position of the uterus, and what are anteversion and retroversion?
The uterus normally lies in anteversion, with the fundus anterior to the cervix. In about 10% of women, the uterus lies in retroversion.
32
What are anteflexion and retroflexion of the uterus?
Anteflexion is when the uterus is curved anteriorly in its longitudinal axis, while retroflexion is when it is curved posteriorly.
33
What are the main parts of the uterus?
The uterus consists of the body or corpus, the isthmus, and the cervix.
34
What are the muscle layers of the corpus uteri?
The corpus uteri has three layers of smooth muscle cells: the external layer with transverse fibers, the middle layer arranged circularly, and the inner layer with longitudinal, circular, and oblique fibers.
35
What is the shape and volume of the uterine cavity in the non-pregnant state?
The uterine cavity is triangular in shape and flattened anteroposteriorly, with a total volume of approximately 2 mL.
36
What lines the uterine cavity?
The uterine cavity is lined by the endometrium, which consists of mucus-secreting columnar epithelium.
37
What is the cervix, and how does it change after vaginal birth?
The cervix is a barrel-shaped structure extending from the external cervical os to the internal cervical os. The external os is round or oval in non-parous women but becomes transverse after vaginal birth.
38
What is the cervical canal, and what epithelium lines it?
The cervical canal is fusiform in shape and is lined by ciliated columnar epithelium that secretes mucus.
39
What is the squamocolumnar junction?
The squamocolumnar junction is the transition point between the ciliated columnar epithelium of the cervical canal and the vaginal ectocervix epithelium.
40
What are nabothian follicles and how do they form?
Nabothian follicles form when cervical glands become obstructed.
41
What is the isthmus of the uterus and its role in pregnancy?
The isthmus joins the cervix to the corpus uteri and enlarges during pregnancy, contributing to the formation of the lower uterine segment.
42
What is the role of the isthmus during labor?
During labor, the isthmus becomes part of the birth canal but does not contribute significantly to fetal expulsion.
43
What does the broad ligament connect, and what does it contain?
The broad ligament connects the lateral uterus, fallopian tubes, and ovaries with the lateral pelvic wall. It contains the ovarian artery and vein, round ligament, fallopian tubes, and ovaries.
44
What is the role of the round ligament, and what does it connect?
The round ligament is responsible for the anteroversion-anteflexion position of the uterus. It connects the uterine horn with the labia majora and contains the lymphatics of the uterine horn.
45
What does the cardinal ligament connect, and what does it contain?
The cardinal ligament connects the cervix with the lateral pelvic wall and contains the uterine artery and vein and the ureter.
46
Where are the fallopian tubes located?
The fallopian tubes are located between the fundus of the uterus and the ovaries, lying on the posterior surface of the broad ligament.
47
What is the length of the fallopian tubes?
The fallopian tubes are approximately 10-12 cm long.
48
What encloses the fallopian tubes, and what does it contain?
The fallopian tubes are enclosed in the mesosalpinx, which contains the blood vessels and nerve supply to the tubes and ovaries.
49
What are the four sections of the fallopian tube?
The fallopian tube is divided into the interstitial portion, isthmus, ampulla, and infundibulum.
50
Where does fertilization typically occur in the fallopian tube?
Fertilization typically occurs in the ampulla, a widened section of the fallopian tube.
51
What lines the fallopian tubes, and what is its function?
The fallopian tubes are lined by a single layer of ciliated columnar epithelium, which assists in the movement of the oocyte.
52
What are the ovaries, and what are their functions?
The ovaries are paired, almond-shaped organs with both reproductive and endocrine functions.
53
What are the dimensions of the ovaries?
The ovaries are approximately 2.5-5 cm in length and 1.5-3.0 cm in width.
54
Where are the ovaries located?
The ovaries lie on the posterior surface of the broad ligament in a shallow depression known as the ovarian fossa.
55
What attaches the anterior border of the ovary to the broad ligament?
The anterior border of the ovary is attached to the posterior layer of the broad ligament by the mesovarium, a fold in the peritoneum.
56
What attaches the lower pole of the ovary to the uterus?
The lower pole of the ovary is attached to the lateral border of the uterus by the ovarian ligament.
57
What covers the surface of the ovary?
The surface of the ovary is covered by cuboidal or low columnar germinal epithelium.
58
What lies beneath the germinal epithelium of the ovary?
Beneath the germinal epithelium is a layer of dense connective tissue known as the tunica albuginea.
59
What are Graafian follicles, and where are they found?
Graafian follicles are found in the highly vascular, central portion of the ovary, known as the medulla.
60
What is the blood supply to the pelvic organs?
The blood supply to the pelvic organs is provided by the internal iliac arteries (hypogastric arteries).
61
What does the internal pudendal artery supply?
The internal pudendal artery supplies the perineum
62
What does the vaginal artery supply, and where can it arise from?
The vaginal artery supplies the anterior and posterior walls of the vagina and can also arise from the uterine artery.
63
What does the uterine artery supply, and what happens during pregnancy?
The uterine artery supplies the body and fundus of the uterus through its superior branch and the cervix and vagina through its cervical branch. During pregnancy, the uterine artery becomes a major vascular structure due to the increase in uterine blood flow.
64
Where does the ovarian artery arise from, and what does it supply?
The ovarian artery arises from the abdominal aorta, crosses the proximal end of the external iliac artery, and supplies the ovary through the suspensory ligament of the ovary.
65
Where do the pelvic lymphatics course and drain?
The pelvic lymphatics course along the internal iliac vessels and drain into the inferior mesenteric and aortic lymph nodes (upper part of rectum), paraaortic lymph nodes (ovaries, fallopian tubes, uterus fundus), and internal and external iliac lymph nodes (uterus body and cervix, bladder, rectum).
66
What do the inferior mesenteric and aortic lymph nodes drain?
They drain the upper part of the rectum.
67
What do the paraaortic lymph nodes drain?
They drain the ovaries, fallopian tubes, and the uterus fundus.
68
What do the internal and external iliac lymph nodes drain?
They drain the uterus body and cervix, bladder, and rectum.
69
What are the autonomic nerves of the pelvis?
The autonomic nerves of the pelvis include the superior and inferior hypogastric plexus, hypogastric nerve, sacral splanchnic nerves, and pelvic splanchnic nerves (S2-S4).
70
What are the functions of the pelvic splanchnic nerves?
The pelvic splanchnic nerves (S2-S4) provide parasympathetic fibers, form part of the pelvic plexus, and innervate the descending and sigmoid colon, pelvic organs, and perineum, including sexual organs.
71
What does the pudendal nerve (S2-S4) provide motor and sensory innervation to?
The pudendal nerve provides motor innervation to the external urethral sphincter, external anal sphincter, and levator ani. It provides sensory innervation to the perineum, clitoris, posterior labia, and anal canal.
72
What injury risks are associated with the pudendal nerve, and what clinical use does it have?
Injury to the pudendal nerve (e.g., during pelvic trauma or surgery) can cause urinary and fecal incontinence. It is also used for pudendal nerve block during childbirth or surgeries involving the perineum, with the ischial spine as the landmark for injection
73
What is the pelvic floor and its role?
The pelvic floor is a diaphragm across the outlet of the true pelvis, supporting some abdominal organs. It is important in defecation, coughing, vomiting, and parturition.
74
What muscles form the principal support of the pelvic floor?
The levator ani muscles, consisting of the iliococcygeus, puborectalis, and pubococcygeus muscles, form the principal support of the pelvic floor.
75
What is the perineum, and how is it divided?
The perineum is the region below the pelvic floor and is divided into anterior (urogenital triangle) and posterior (anal triangle) sections by a line between the ischial tuberosities.
76
What structures are found in the urogenital triangle of the perineum?
The urogenital triangle includes part of the urethra and the urogenital diaphragm, which is traversed by the vagina.
77
What structures are found in the anal triangle of the perineum?
The anal triangle includes the anus, anal sphincter, and perineal body
78
What passes through the lateral aspect of the fossa in the perineum?
The pudendal nerve and internal pudendal vessels pass through the lateral aspect of the fossa, enclosed in the fascial layer of Alcock’s canal.
79
What forms the cortex of the ovary during oogenesis?
Germ cells form sex cords that become the cortex of the ovary, which breaks up into separate clumps of cells by 16 weeks, becoming primary follicles that incorporate central germ cells.
80
How many oogonia are present by 20 weeks of intrauterine life?
By 20 weeks, there are approximately 7 million oogonia.
81
What happens to oogonia after 20 weeks of intrauterine life?
No further cell division occurs after 20 weeks, and no more ova are produced. The oogonia begin the first meiotic division, becoming primary oocytes by birth.
82
How does the number of primary oocytes change from birth to puberty?
By birth, there are about 1 million primary oocytes, and this number decreases to approximately 0.4 million by puberty.
83
What cells surround the oogonia in the cortex of the ovary?
The oogonia are surrounded by follicular cells that later develop into granulosa cells.
84
What characterizes the first stage of follicular development in the ovary?
The first stage is characterized by the enlargement of the ovum and the aggregation of stromal cells to form thecal cells.
85
When is a dominant follicle selected, and what structure forms around the ovum?
A dominant follicle is selected around day 6 of the menstrual cycle, and the innermost granulosa cells adhere to the ovum, forming the corona radiata.
86
What is the zona pellucida, and when does it form?
The zona pellucida is a clear layer of gelatinous material that collects around the ovum during follicular development.
87
What happens to the follicle after ovulation if implantation does not occur?
The corpus luteum reaches its peak about 7 days after ovulation and regresses unless implantation occurs. If not, it becomes a white scar known as the corpus albicans.
88
What hormone produced by an implanting embryo prolongs corpus luteum function?
β-hCG (human chorionic gonadotropin) produced by the implanting embryo prolongs corpus luteum function until the placenta takes over at about 10 weeks of gestation.
89
What initiates the hormonal events associated with ovulation?
The release of GnRH (gonadotropin-releasing hormone) initiates the hormonal events, resulting in the release of FSH (follicle-stimulating hormone) and LH (luteinizing hormone) from the pituitary.
90
How does GnRH influence LH and oestrogen levels during the menstrual cycle?
GnRH is released in episodic surges, which increase plasma LH levels just before midcycle, initiating the oestrogen-induced LH surge.
91
How do FSH levels change during the menstrual cycle?
FSH levels are slightly higher during menses and subsequently decline due to the negative feedback effect of oestrogen production by the dominant follicle.
92
When does the LH surge occur in relation to ovulation?
The LH surge occurs 35–42 hours before ovulation, accompanied by a smaller coincidental FSH peak.
93
What happens to LH and FSH levels in the second half of the menstrual cycle?
LH and FSH levels are slightly lower in the second half of the cycle, but continued LH release is necessary for normal corpus luteum function.
94
How do estrogen and progesterone levels change during the menstrual cycle?
Estrogen increases during the first half of the cycle, falls to about 60% of its follicular phase peak after ovulation, and rises again during the luteal phase.
Progesterone levels are low before ovulation but increase throughout most of the luteal phase.
95
What regulates the release of FSH and LH by the pituitary?
Feedback mechanisms involving estrogen and progesterone from the ovaries regulate the release of FSH and LH. In cases of ovarian failure, such as menopause, the lack of these hormones leads to elevated gonadotrophin levels.
96
What are the functions of FSH and LH during the menstrual cycle?
FSH stimulates follicular growth and development, specifically binding to granulosa cells. It helps the dominant follicle mature by stimulating estrogen production and inducing LH receptors in granulosa cells.
LH triggers ovulation, reactivates meiosis I in the oocyte, and supports corpus luteum development.
97
What happens to the follicles during a menstrual cycle?
Around 30 follicles begin to mature during each cycle, but only one dominant follicle becomes fully developed. The dominant follicle continues developing under the influence of FSH, while other follicles degenerate due to lower FSH levels.
98
What is the role of LH receptors in the menstrual cycle?
LH receptors are found in the theca and granulosa cells of the developing follicle and later in the corpus luteum. LH binds to these receptors to:
Trigger ovulation, allowing the oocyte to be released from the follicle.
Reactivate meiosis I in the oocyte, which had been arrested.
Sustain the development and function of the corpus luteum, which secretes progesterone to support a potential pregnancy.
99
Endometrial Cycle Phases
Menstrual Phase
Phase of Repair
Follicular/Proliferative Phase
Luteal/Secretory Phase
100
Endometrial Cycle Menstrual Phase
(Days 1-4):
The outer two layers of the endometrium (zona compacta and zona spongiosa) are shed due to the vasoconstriction of spiral arterioles, leading to necrosis. This phase is triggered by a fall in estrogen and progesterone.
101
Endometrial Cycle Phase of Repair
(Days 4-7):
A new capillary bed forms, and the epithelial surface regenerates. This prepares the endometrium for the next cycle.
102
Endometrial Cycle Follicular/Proliferative Phase
(Days 7-14):
The endometrium undergoes maximal growth, with elongation and expansion of the endometrial glands and stromal development.
This phase is driven by rising estrogen levels, which stimulate growth until ovulation.
103
Endometrial Cycle Luteal/Secretory Phase
(Days 15-28):
After ovulation, the endometrium becomes more glandular and secretory in response to progesterone produced by the corpus luteum. The glands become convoluted with a "saw-toothed" appearance, and there is basal vacuolation in epithelial cells.
As menstruation approaches, there is stromal edema and infiltration of leukocytes, preparing the endometrium for its shedding unless pregnancy occurs.
104
105
What is fertilization?
Fertilization is the fusion of male and female gametes to produce a diploid genetic complement from both partners.
106
What is sperm transport and how is it influenced by the female cycle?
Sperm migrate into the cervical mucus after semen deposition near the cervical os. Migration is facilitated by receptive mucus in mid-cycle, but during the luteal phase, the mucus is not receptive, limiting sperm access to the uterine cavity.
107
What is the rate of sperm migration under favorable conditions?
Sperm migrate at a rate of 6 mm per minute under favorable conditions.
108
What is capacitation and where does it occur?
Capacitation is the final maturation process of sperm, allowing penetration of the zona pellucida, and occurs during passage through the Fallopian tubes.
109
What triggers the acrosome reaction during fertilization?
The adherence of sperm to the oocyte triggers the acrosome reaction, leading to the release of lytic enzymes that help sperm penetrate the oocyte membrane.
110
How is the sperm head incorporated into the oocyte?
The sperm head fuses with the oocyte plasma membrane and is engulfed by phagocytosis into the oocyte, where it decondenses to form the zygote.
111
What happens to the conceptus 36 hours after fertilization?
The conceptus is transported through the Fallopian tube by muscular peristaltic action and undergoes cleavage. By the 16-cell stage, it becomes a solid ball of cells called the morula.
112
What structure forms after the morula and when does it attach to the endometrium?
A blastocyst forms after the morula, and six days after ovulation, it attaches to the endometrium, usually near the mid-portion of the uterine cavity.
113
What occurs by the seventh post-ovulatory day in the process of implantation?
The blastocyst penetrates deeply into the endometrium. Endometrial cells are destroyed by the cytotrophoblast, initiating the decidual reaction, where stromal cells become large and pale.
114
3. What is the weight change of the uterus from non-pregnancy to term?
The non-pregnant uterus weighs ~40–100 g, increasing during pregnancy to 300–400 g at 20 weeks and 800-1000 g at term.
115
What is the structure of the uterus during pregnancy?
The uterus consists of bundles of smooth muscle cells separated by thin sheets of connective tissue composed of collagen, elastic fibers, and fibroblasts. These all hypertrophy during pregnancy.
116
How does myometrial growth occur during pregnancy?
Myometrial growth occurs almost entirely due to muscle hypertrophy and elongation of the cells from 5 µm in the non-pregnant state to 200–600 µm at term. This is influenced by estrogen and progesterone.
117
What are the three functional and morphological divisions of the uterus?
The uterus is divided into three sections:
Cervix
Isthmus
Body of the uterus (corpus uteri).
118
What percentage of uterine muscle cells are in the cervix?
The cervix contains only 10% of uterine muscle cells, with 80% of its total protein in the non-pregnant state consisting of collagen.
119
What happens to the collagen content of the cervix by the end of pregnancy?
By the end of pregnancy, the collagen concentration in the cervix is reduced to one-third of its pre-pregnancy levels.
120
What are the characteristic changes in the cervix during pregnancy?
The characteristic changes include:
Increased vascularity
Hypertrophy of cervical glands
Increased mucous secretion, forming an antibacterial mucus plug
Reduction in collagen, accumulation of glycosaminoglycans and water, leading to cervical ripening.
121
What changes occur in the isthmus of the uterus during pregnancy?
By the 28th week, regular contractions stretch and thin the isthmus, resulting in the early formation of the lower uterine segment, which is fully formed during labor.
122
Why is the lower uterine segment the preferred site for a caesarean delivery?
Due to its relative avascularity and quiescence in the puerperium, the lower uterine segment is the ideal site for a caesarean delivery incision.
123
How does the corpus uteri change during pregnancy?
The corpus uteri changes in size, shape, position, and consistency. The fundus enlarges, the round ligaments emerge from a relatively lower point, and the uterus transforms from pear-shaped to globular and ovoid.
124
What is the capacity of the uterine cavity at full term?
The uterine cavity expands from around 4 mL to 4000 mL at full term.
125
How do the uterine arteries change during pregnancy?
The uterine arteries dilate, and the arcuate arteries supplying the placental bed become 10 times larger. Spiral arterioles increase to 30 times their pre-pregnancy diameter.
126
How much does uterine blood flow increase during pregnancy?
Uterine blood flow increases from 50 mL/min at 10 weeks gestation to 500–600 mL/min at term.
127
What is the contribution of the ovarian vessels to uterine blood supply during pregnancy?
In pregnancy, 20–30% of the blood supply to the uterus is contributed by the ovarian vessels.
128
How many spiral arterioles deliver blood to the intervillous space?
There are 100–150 spiral arterioles delivering blood to the intervillous space during pregnancy.
129
What is essential for the continuation of a successful pregnancy?
The myometrium must remain quiescent until the fetus is mature and capable of sustaining extrauterine life.
130
How does the myometrium remain quiescent during pregnancy despite uterine distention?
The pregnant myometrium has greater compliance, and progesterone maintains quiescence by increasing the resting membrane potential of myometrial cells.
131
What role does progesterone play in uterine quiescence?
Progesterone increases the resting membrane potential of myometrial cells, helping to maintain quiescence and prevent labor.
132
What can induce labor from the first trimester by antagonizing progesterone?
Progesterone antagonists, such as mifepristone, can induce labor from the first trimester.
133
What are other mechanisms that contribute to uterine quiescence?
Locally generated nitric oxide and relaxatory hormones like prostacyclin (PGI2), prostaglandin (PGE2), and calcitonin gene-related peptide also contribute to maintaining uterine quiescence.
134
When does measurable uterine activity begin during pregnancy?
Uterine activity can be measured as early as 7 weeks gestation, with frequent, low-intensity contractions.
135
How do uterine contractions change throughout pregnancy?
Contractions increase in intensity but remain low frequency in the second trimester. In the third trimester, they increase in both frequency and intensity, leading up to labor.
136
What are Braxton Hicks contractions?
Braxton Hicks contractions are painless uterine tightenings that occur during pregnancy, do not produce cervical dilation, and are not associated with labor.
137
How does the vaginal epithelium change during pregnancy?
The vagina's stratified squamous epithelium hypertrophies during pregnancy.
138
What happens to the vaginal musculature and connective tissue during pregnancy?
The vaginal musculature becomes hypertrophic, connective tissue collagen decreases, while water and glycosaminoglycans increase.
139
Why does the vagina have a slightly bluish appearance during pregnancy?
The rich venous vascular network in the vaginal walls becomes engorged, giving the vagina a bluish appearance.
140
What is the vaginal pH during pregnancy and its significance?
Vaginal pH falls to 3.5–4.0, which helps prevent bacterial infections, but increases the risk of yeast infections, such as Candida.
141
When do cardiovascular system changes begin during pregnancy?
Cardiovascular system adaptations begin in the luteal phase of every ovulatory cycle, and most changes are almost complete by 12–16 weeks gestation.
142
How does the heart's position and size change during pregnancy?
As the uterus grows, the diaphragm pushes the heart upwards and left laterally (~15% deviation). The heart also enlarges by 70–80 mL due to increased venous filling and slight wall thickening.
143
What ECG changes are commonly seen due to the heart's displacement during pregnancy?
There is an inverted T wave in lead III and a Q wave in leads III and aVF.
144
How does cardiac output change during pregnancy?
Cardiac output rises, with most of the increase (1.5 L/min) occurring in the first 14 weeks. It increases from 4.5 L/min to 6.0 L/min and can rise by another 2 L/min during labor.
145
How does heart rate and stroke volume change during pregnancy?
Heart rate increases by 10–15 beats/min by mid-pregnancy, and stroke volume rises from about 64 to 71 mL during the first trimester.
146
What is supine hypotension syndrome in late pregnancy?
Supine hypotension syndrome occurs when the mother lies on her back, causing compression of the inferior vena cava, restricting venous return from the lower limbs, and leading to a profound fall in stroke volume and blood pressure.
147
How does the pulmonary circulation adapt to increased blood flow during pregnancy?
The pulmonary circulation absorbs high rates of blood flow without an increase in pressure. Pulmonary resistance falls early in pregnancy and remains low, so pressure in the right ventricle and pulmonary arteries does not change.
148
How does red cell mass change during pregnancy?
There is a steady increase in red cell mass throughout pregnancy, rising from ~1400 mL to ~1700 mL. However, haemoglobin concentration, haematocrit, and red cell count fall because plasma volume increases proportionately more.
149
What happens to plasma folate concentration during pregnancy?
Plasma folate concentration halves by term due to greater renal clearance.
150
What changes occur in white blood cells during pregnancy?
The total WBC count increases, primarily due to a rise in neutrophil polymorphonuclear leukocytes, peaking at 30 weeks. Neutrophilia occurs during labor and after delivery, while eosinophils decrease during labor and are virtually absent at delivery. Lymphocyte count remains constant.
151
How do platelet numbers and reactivity change during pregnancy?
Platelet numbers fall, possibly due to dilution, while platelet volume increases from ~28 weeks. Platelet reactivity increases during the second and third trimesters and remains elevated until ~12 weeks after delivery.
152
What changes occur in clotting factors during pregnancy?
There is an increased tendency toward clotting, which may protect against hemorrhage during labor. Factors VII, VIII, VIII:C, X, and IX increase, while factors II and V remain constant. Plasma fibrinogen rises from 2.5–4.0 g/L to as high as 6.0 g/L in late pregnancy, and the ESR increases due to higher fibrinogen levels.
153
How does respiratory function change during pregnancy?
The diaphragm rises and the intercostal angle increases, while residual volume decreases slightly and vital capacity increases slightly. Inspiratory capacity increases by ~300 mL, while residual volume decreases by about 300 mL, improving gas mixing.
154
How does tidal volume and respiratory rate change during pregnancy?
Tidal volume increases from ~500 mL to ~700 mL by late pregnancy, while the respiratory rate remains constant at 14–15 breaths/min.
155
Why does CO2 production increase in the third trimester?
CO2 production rises sharply during the third trimester due to increased fetal metabolism. Low maternal PaCO2 facilitates efficient placental transfer of CO2 from the fetus.
156
How does alveolar ventilation change during pregnancy?
Alveolar ventilation increases, causing a small rise in maternal PO2. The rightward shift in the maternal oxyhemoglobin dissociation curve, caused by increased 2,3-DPG in erythrocytes, facilitates oxygen unloading to the fetus.
157
What is the overall increase in oxygen consumption by term during pregnancy?
Oxygen consumption increases by ~16% by term due to growing maternal and fetal metabolic demands.
158
4. What happens to renal parenchymal volume during pregnancy?
Renal parenchymal volume increases by 70% by the third trimester, with marked dilatation of the calyces, renal pelvis, and ureters, leading to increased renal size. These changes occur in the first trimester due to the influence of progesterone.
159
What is vesicoureteric reflux and its significance during pregnancy?
Vesicoureteric reflux occurs sporadically during pregnancy and, combined with ureteric dilatation, is associated with a high incidence of urinary stasis and urinary tract infections.
160
How does renal blood flow (RBF) change during pregnancy?
Renal blood flow increases by 50–80% in the first trimester, is maintained during the second trimester, and falls by ~15% thereafter.
161
What changes occur in glomerular filtration rate (GFR) during pregnancy?
The glomerular filtration rate (GFR) increases significantly, with a 25% increase in 24-hour creatinine clearance 4 weeks after the last menstrual period and a 45% increase at 9 weeks.
162
What happens to plasma volume during pregnancy?
Plasma volume increases to a peak between 32 and 34 weeks, with a total increase of ~50% in a first pregnancy and 60% in subsequent pregnancies.
163
What changes in glucose excretion are common during pregnancy?
Glucose excretion increases during pregnancy, and intermittent glycosuria is common in normal pregnancies, unrelated to blood glucose levels.
164
What happens to protein and albumin excretion during pregnancy?
Both total protein and albumin excretion rise during pregnancy, with an accepted upper limit of 200 mg total protein excretion per 24 hours by at least 36 weeks.
165
How is gastric function altered during pregnancy?
Gastric secretion decreases, gastric motility is low, and gastric emptying is delayed. Decreased motility also occurs in the small and large bowel, with increased colonic absorption of water and sodium leading to constipation.
166
What causes heartburn in pregnant women?
Heartburn is common and may be related to the displacement of the lower esophageal sphincter (LES) through the diaphragm and its decreased response as intra-abdominal pressure rises.
167
How does hepatic synthesis change during pregnancy?
Hepatic synthesis of albumin, plasma globulin, and fibrinogen increases under the stimulation of estrogen.
168
What changes occur in maternal carbohydrate metabolism during pregnancy?
By 6–12 weeks gestation, fasting plasma glucose concentrations fall to about 0.5–1 mmol/L. The mother’s plasma insulin concentrations rise, and pregnant women develop insulin resistance, leading to increased insulin production in response to glucose.
169
What happens to total protein concentration during pregnancy?
Total protein concentration falls by about 1 g/dL during the first trimester, from 7 g/dL to 6 g/dL, despite increased nitrogen retention.
170
How do amino acid levels change during pregnancy?
Amino acid levels, apart from alanine and glutamic acid, decrease below normal values, as there is active transport of amino acids to the fetus for protein synthesis and gluconeogenesis.
171
What changes occur in lipid levels during pregnancy?
Total serum lipid concentration rises from about 600 to 1000 mg/100 mL, with threefold increases in VLDL triglycerides and a 50% increase in VLDL cholesterol by 36 weeks.
172
How are birth weight and maternal lipid levels related during pregnancy?
Birth weight and placental weight are directly related to maternal VLDL triglyceride levels at term.
173
What happens to plasma calcium levels during pregnancy?
Total plasma calcium decreases because albumin concentrations fall, but unbound ionized calcium remains unchanged. Gastrointestinal calcium absorption doubles by 24 weeks of pregnancy.
174
What is the average weight gain during pregnancy for a woman with a normal BMI?
The average weight gain during pregnancy in a woman of normal BMI is approximately 12.5 kg.
175
What are the average weekly weight gain rates during different trimesters of pregnancy?
Up to 18 weeks: 0.3 kg/week
18 to 28 weeks: 0.5 kg/week
After 28 weeks: ~0.4 kg/week
176
What contributes to the increase in weight during pregnancy?
Much of the weight increase arises from water retention, with a mean total increase of approximately 8.5 L, common in both primigravid and multiparous women.
177
What effect does increased hydration of connective tissue have during pregnancy?
Increased hydration results in laxity of the joints, particularly in the pelvic ligaments and the pubic symphysis.
178
What complications can arise from excessive weight gain during pregnancy?
Acute excessive weight gain may be associated with the development of preeclampsia, whereas mild edema is generally associated with a good fetal outcome.
179
What are the consequences of failure to gain weight during pregnancy?
Failure to gain weight may be associated with reduced amniotic fluid volume, small placental size, impaired fetal growth, and adverse pregnancy outcomes.
180
What happens to a woman's weight immediately after delivery?
Immediately following delivery, there is a weight loss of approximately 6 kg due to water and fluid loss, as well as the loss of the products of conception.
181
How does body weight change in the postpartum period?
From day 3, body weight falls by ~0.3 kg/day until day 10, stabilizing by week 10 at ~2.3 kg above pre-pregnancy weight (or 0.7 kg for lactating women).
182
What percentage of women retain 5 kg or more of pregnancy-related weight gain after 6–18 months?
About one-fifth of women retain 5 kg or more of pregnancy-related weight gain after 6–18 months.
183
What early changes occur in the breasts during pregnancy?
Early signs include breast tenderness, increased size, enlargement of the nipples, and increased vascularity and pigmentation of the areola.
184
What is the role of Montgomery’s tubercles during pregnancy?
Montgomery’s tubercles are sebaceous glands in the areola that hypertrophy during pregnancy and are richly supplied with sensory nerves, facilitating suckling reflexes.
185
What hormones stimulate ductal proliferation during pregnancy?
High concentrations of estrogen, along with growth hormone and glucocorticoids, stimulate ductal proliferation during pregnancy.
186
What is colostrum, and when can it be expressed?
Colostrum is a thick, glossy, protein-rich fluid that can be expressed from the breast starting from 3 to 4 months of pregnancy and for the first 30 hours after delivery.
187
What inhibits full lactation during pregnancy?
High levels of estrogen and progesterone block the alveolar transcription of α-lactalbumin, inhibiting full lactation during pregnancy.
188
What initiates lactation after delivery?
Prolactin stimulates the synthesis of milk components. The sudden reduction of progesterone and estrogen after delivery allows prolactin to act unhindered, and suckling promotes its release.
189
How much milk is typically produced daily during breastfeeding, and what are the caloric needs for the mother?
500–1000 mL of milk are produced daily, requiring about 500 kcal extra per day, with an additional 250 kcal/day coming from maternal fat stores.
190
What role does oxytocin play in breastfeeding?
Suckling promotes the release of oxytocin, which stimulates the myoepithelial cells to contract, resulting in the milk-ejection reflex. This reflex can also be stimulated by the mother seeing or hearing the infant or thinking about feeding.
191
What is chloasma and where does it typically appear during pregnancy?
Chloasma is the appearance of melanocyte-stimulating hormone (MSH)-stimulated pigmentation on the face, areola of the nipples, and the linea alba of the anterior abdominal wall, giving rise to the linea nigra.
192
What are stretch marks (striae gravidarum), and what causes them during pregnancy?
Stretch marks are disruptions of collagen fibers in the subcuticular zone, predominantly occurring on the abdominal wall, thighs, and breasts. They are more related to increased production of adrenocortical hormones than to the tension in skin folds due to abdominal expansion.
193
What role does human chorionic gonadotropin (hCG) play in pregnancy?
hCG is the hormone that signals pregnancy and supports the early stages by maintaining the corpus luteum and stimulating the production of progesterone and estrogen.
194
What hormones are synthesized by the fetoplacental unit during pregnancy?
The fetoplacental unit synthesizes large amounts of estrogen and progesterone, essential for uterine growth, quiescence, and breast development.
195
How does estrogen affect the synthesis of binding globulins?
Estrogen stimulates the synthesis of binding globulins for thyroxine and corticosteroids, vascular endothelial growth factor (VEGF), and promotes angiogenesis.
196
What hormones does the anterior pituitary produce during pregnancy, and what is their significance?
The anterior pituitary produces LH, FSH, TSH, GH, ACTH, and prolactin. Increased estrogen levels stimulate the lactotrophs, leading to rising prolactin levels, crucial for lactation.
197
What triggers the release of oxytocin from the posterior pituitary, and what is its role?
Oxytocin is released in response to cervical dilation, reinforcing uterine contractions during labor. It enhances uterine sensitivity to oxytocin due to upregulation of oxytocin receptors.
198
What is the role of corticotropin-releasing hormone (CRH) in pregnancy?
CRH stimulates the release of ACTH, and its plasma levels increase significantly in the third trimester, possibly triggering the onset of labor.
199
What changes occur in the thyroid gland during pregnancy?
The thyroid gland enlarges in up to 70% of pregnant women, with increased uptake of iodide and urinary excretion, leading to relative iodine deficiency but not affecting T3, T4, and TSH levels crossing the placenta.
200
What happens to parathyroid hormone (PTH) levels during pregnancy?
There is a fall in intact PTH levels, but a doubling of 1,25-dihydroxy vitamin D occurs. Placentally derived PTH-related protein also influences calcium homeostasis.
201
How does the renin-angiotensin system respond during pregnancy?
The renin-angiotensin system is activated in the luteal phase and is one of the first hormonal responses to recognize pregnancy, playing a role in regulating blood pressure and fluid balance.
202
5. What is the decidual reaction, and what does it involve?
The decidual reaction (decidualization) is the transformation of the endometrium following implantation, characterized by thickening and structural changes, resulting in the formation of decidua, which nourishes the embryo until the placenta forms.
203
What are the main functions of the decidua during pregnancy?
The decidua provides histiotrophic nutrition (storage of fat and glycogen), offers immune privilege, and prepares for placental circulation by transforming decidual vessels into a network of anastomosing spiral arteries under progesterone influence.
204
Name the three distinct parts of the decidua and their functions.
1. Decidua basalis: Maternal portion of the placenta.
2. Decidua capsularis: Covers the blastocyst after implantation, appearing cap-like.
3. Decidua parietalis: Lines the uterus elsewhere than at the implantation site.
205
What is placentation?
Placentation refers to the development of the placenta, which consists of an embryonic portion derived from trophoblast cells and a maternal portion derived from the decidua basalis.
206
Describe the prelacunar stage of early placental development.
The prelacunar stage lasts until approximately day 9 of embryogenesis and involves initial implantation without the formation of blood-filled lacunae.
207
What occurs during the lacunar stage of placental development?
From approximately day 9, lacunae form in the syncytiotrophoblast, eroding spiral arteries, which fills the lacunae with maternal blood. This stage leads to the merging of lacunae to form the intervillous space and the establishment of hemotrophic nutrition.
208
What is the significance of the early villous stage in placental development?
The early villous stage occurs from days 13 to 28 of embryogenesis, during which chorionic villi develop and mature, facilitating the exchange of nutrients between maternal and fetal blood.
209
Explain the development and structure of primary villi.
Primary villi develop from the migration of cytotrophoblast cells into syncytiotrophoblast trabeculae.
Their structure includes an inner layer of cytotrophoblast and an outer layer of syncytiotrophoblast cells with microvilli, which are in direct contact with maternal blood.
210
How do secondary villi differ from primary villi?
Secondary villi develop when extraembryonic mesoderm cells migrate into the center of primary villi, creating a structure with a mesenchymal core, an inner layer of cytotrophoblast, and an outer layer of syncytiotrophoblast cells with microvilli.
211
What characterizes tertiary villi (terminal villi), and when do they develop?
Tertiary villi, or terminal villi, develop around the third week of pregnancy when they connect to umbilical cord vessels. After the fourth month, they undergo vascularization, and isolated cytotrophoblast cells (Langhans cells) remain.
212
Describe the structure of terminal villi.
Terminal villi consist of a mesenchymal core with fetal capillaries, an inner layer of isolated cytotrophoblast cells (Langhans cells), and an outer layer of syncytiotrophoblast cells with microvilli, facilitating maternal-fetal exchange.
213
What is the average weight, thickness, and diameter of a mature placenta at the end of pregnancy?
A mature placenta weighs approximately 500 g, is about 2 cm thick, and has a diameter of 15–20 cm.
214
What are the three main parts of the placenta?
1. Basal Plate (Decidual Basalis)
2. Intervillous Space and Villous Trees (Fetomaternal Zone)
3. Chorionic Plate (Fetal Component)
215
Describe the structure and function of the basal plate (decidual basalis).
The basal plate is the maternal component of the placenta, abutting the uterine wall. It consists of maternal decidua with ingrown embryonal cells (cytotrophoblast, syncytiotrophoblast, and extravillous trophoblast cells) and is supplied by uterine spiral arteries.
It contains placental septa and cotyledons, which are distinct areas facing the uterine wall.
216
What is the role of the intervillous space in the placenta?
The intervillous space is the contact zone between maternal and fetal placental structures, filled with maternal blood and containing protruding villous trees. It is the site of fetomaternal gas and nutrient exchange.
217
Define the components of villous trees in the placenta.
Villous trees are composed of:
Stem Villi: Basal region containing fetal arteries and veins.
Intermediate Villi: Containing fetal arterioles, venules, and capillaries.
Terminal Villi: Tertiary villi that float freely in the intervillous space, directly involved in gas and nutrient exchange.
Anchoring Villi: Anchor the villous trees to the decidua, expanding cytotrophoblast positioned between the decidua and syncytiotrophoblast.
218
What comprises the chorionic plate of the placenta?
The chorionic plate is formed by the syncytiotrophoblast, cytotrophoblast, and the somatic layer of the extraembryonic mesoderm.
It includes the chorion frondosum (with villi, involved in placenta formation) and chorion laeve (outer layer without villi).
219
What layers constitute the placental barrier until the 4th month of development?
The placental barrier until the 4th month consists of the following layers (from maternal to fetal):
1. Syncytiotrophoblast
2. Cytotrophoblast
3. Basal lamina of trophoblasts
4. Villous stroma (connective tissue)
5. Basal lamina of the endothelium
6. Capillary endothelium
220
How does the placental barrier change after the 4th month of development?
After the 4th month, the structure of the placental barrier (from maternal to fetal) changes to:
1. Syncytiotrophoblast
2. Fused basal lamina from trophoblasts and endothelium
3. Capillary endothelium
The cytotrophoblast disappears from the villous wall, leaving only isolated cytotrophoblast cells (Langhans cells).
221
Why is it important to inspect the placenta after birth?
Inspecting the placenta after birth is crucial to ensure it has completely detached from the uterine wall. Incomplete detachment can lead to postpartum hemorrhage.
The completeness of all placental cotyledons should be verified, and the fetal side should be covered by the amnion.
222
Where are pregnancy hormones produced?
Pregnancy hormones are produced by the syncytiotrophoblast.
223
What are the primary functions of hormones produced during pregnancy?
The primary functions include:
Continuation of pregnancy
Maternal adaptation to pregnancy
Regulation of uterine circulation
Fetal development and growth
Inducing birth
224
What is the role of human chorionic gonadotropin (hCG)?
hCG is responsible for:
Continuation of pregnancy
Formation and maintenance of the corpus luteum graviditatis
Maximum concentration occurs around the 10th week of pregnancy.
225
What does human placental lactogen (hPL) do?
hPL promotes:
Fetal growth and development
Increased insulin tolerance in the mother
Constant increase until 34 weeks (end of placental growth).
226
What is the function of corticotropin-releasing hormone (CRH) during pregnancy?
CRH functions include:
Determining the duration of gestation
Maturation of the fetal lung
Stimulation of surfactant production
Increased levels during pregnancy or maternal stress.
227
What role does estrogen play in pregnancy?
Estrogen is responsible for:
Production by the corpus luteum until week 10, then by the fetal adrenal cortex.
Stimulating growth (anabolic effects)
Increasing uterine wall thickness
Promoting proliferation and differentiation of mammary glands
Levels increase continuously until after birth.
228
What is the role of progesterone in pregnancy?
Progesterone is responsible for:
Production by the corpus luteum until week 10, then by the placenta.
Optimizing the zygote environment in the fallopian tube and aiding implantation
Maintaining pregnancy
Transforming the endometrium
Preventing menstruation
Closing the cervix and increasing viscosity
Inhibiting uterine contractions.
229
How does gas exchange occur between maternal and fetal blood?
Gas exchange occurs primarily through passive transport:
Diffusion: O2 (due to higher affinity of fetal HbF), CO2, creatinine, urea, bilirubin, water, and drugs.
Facilitated diffusion: Glucose and lactate.
230
What are the active transport mechanisms in the placenta?
Active transport mechanisms include:
Amino acids, peptides, hormones, vitamins, fatty acids, and inorganic ions.
Pinocytosis: Allows transfer of proteins, lipids, and antibodies (IgG).
231
Which substances have limited ability to cross the placental barrier?
Fat-soluble vitamins (A, D, E, K), immunoglobulins (except IgG), and most proteins typically have limited ability to cross the placental barrier.
232
What is unique about Anti-D antibodies in relation to the placenta?
Anti-D antibodies from the Rh system can cross the placental barrier, providing passive immunity.
233
What is the structure of the umbilical cord?
The umbilical cord typically contains:
2 umbilical arteries: Carry deoxygenated blood from the fetus to the placenta.
1 umbilical vein: Carries oxygenated, nutrient-rich blood from the placenta to the fetus.
234
When does the development of the umbilical cord begin?
The development of the umbilical cord begins around the 3rd week of embryogenesis and is approximately 50–70 cm long by the end of pregnancy.
235
What is the connecting stalk in the umbilical cord's early development?
The connecting stalk is a precursor to the mature umbilical cord, containing:
Allantois: A small sac-like structure involved in fetal bladder development.
Vitelline duct: Connects the midgut to the yolk sac; obliterates by the 7th week.
236
What is Wharton's jelly, and what is its function?
Wharton's jelly is a gelatinous connective tissue in the umbilical cord that prevents bending of the cord, ensuring stable blood flow to and from the fetus.
237
What are the remnants found in the late stage of umbilical cord development?
In the late stage of development, the umbilical cord contains:
Urachus: A duct between the fetal bladder and umbilicus.
Remnant of the allantois, which obliterates after birth to form the median umbilical ligament.
238
6. What occurs in fetal development during the first 10 weeks of gestation?
During the first 10 weeks, there is a massive increase in cell numbers in the developing embryo, but the actual gain in weight is small.
239
When does rapid weight gain occur in fetal development?
Rapid weight gain occurs after 10 weeks of gestation, leading to a full-term fetal weight of around 3.5 kg.
240
How is protein accumulated in the fetus?
Protein accumulation occurs throughout pregnancy, supporting growth and development of fetal tissues.
241
Where are fat stores located in the fetus, and how do they change throughout gestation?
Brown fat is stored around the neck, behind the scapulae, sternum, and kidneys.
White fat forms subcutaneous fat covering the body.
Fat stores make up 1% of body weight at 24–28 weeks and increase to 15% by 35 weeks.
242
What factors determine actual fetal size?
Factors that determine fetal size include:
Efficiency of the placenta
Adequacy of uteroplacental blood flow
Genetic and racial factors
243
What factors determine fetal birth weight?
Fetal birth weight is influenced by:
Gestational age
Race
Maternal height and weight
Parity (number of pregnancies)
244
What are the characteristics of the fetus at 12 weeks gestation?
At 12 weeks:
Skin is translucent with no subcutaneous fat; blood vessels are visible.
Upper limbs have reached their final relative length.
External genitals are distinguishable but remain undifferentiated.
245
What is the fetal crown-rump length at 16 weeks gestation?
At 16 weeks, the crown-rump length is approximately 122 mm and the external genitalia can now be differentiated.
246
What are the key characteristics of the fetus at 24 weeks gestation?
At 24 weeks:
Crown-rump length is 210 mm.
Eyelids are separated.
Skin is opaque but wrinkled due to lack of subcutaneous fat.
Fine hair covers the body.
247
What changes occur in the fetus by 28 weeks gestation?
By 28 weeks:
The eyes are open.
Scalp hair begins to grow.
248
How does the fetal heart develop by 4–5 weeks gestation?
By 4–5 weeks, the heart develops initially as a single tube, and a heartbeat is detectable at a rate of 65 beats/min.
249
When does the definitive circulation develop in the fetus, and what is the heart rate at that time?
Definitive circulation develops by 11 weeks gestation, with the heart rate increasing to approximately 140 beats/min.
250
What percentage of venous return enters the left atrium through the foramen ovale in the mature fetus?
About 40% of the venous return entering the right atrium flows directly into the left atrium through the foramen ovale.
251
How does fetal cardiac output work in the mature fetus?
Fetal cardiac output is estimated at 200 mL/min/kg body weight and is entirely dependent on heart rate, not stroke volume.
252
When can fetal respiratory movements first be detected, and when is a regular pattern established?
Fetal respiratory movements can be detected from 12 weeks gestation, with a regular respiratory pattern established by mid-trimester.
253
What is the respiratory rate of the fetus at 34 weeks gestation?
At 34 weeks gestation, respiration occurs at a rate of 40–60 movements/min with periods of apnea in between.
254
How do fetal respiratory movements affect the amniotic fluid?
Fetal breathing results in shallow movements, causing amniotic fluid to move into the bronchioles and occasionally deeper into the bronchial tree but not into the alveoli due to high pressure from alveolar fluid secretion.
255
What might cause inhalation of amniotic fluid into the alveoli?
Inhalation of amniotic fluid into the alveoli may occur during episodes of hypoxia, leading to gasping.
256
What stimulates fetal breathing, and what factors reduce it?
Fetal breathing is stimulated by hypercapnia and elevated maternal glucose levels. Hypoxia and maternal smoking reduce the frequency of fetal breathing.
257
How long can periods of fetal apnea last as term approaches?
Fetal apnea can increase towards term, lasting for as long as 120 minutes in a normal fetus.
258
What types of cells line the fetal pulmonary alveoli, and what are their functions?
The fetal pulmonary alveoli are lined by:
Type I cells: involved in gas exchange.
Type II cells: secrete surfactant to maintain the functional patency of the alveoli.
259
What are the principal surfactants produced by type II cells, and when do they reach functional levels?
The principal surfactants are sphingomyelin and lecithin. Production of lecithin reaches functional levels by 32 weeks gestation, though it may begin as early as 24 weeks.
260
How can the maturity of the fetal lungs be assessed?
The measurement of lecithin concentration in the amniotic fluid is a useful method for assessing functional fetal lung maturity.
261
What marks the onset of gut function in the developing fetus?
By 16–20 weeks gestation, mucosal glands appear, indicating the earliest onset of gut function.
262
When do most digestive enzymes appear in the fetus?
By 26 weeks gestation, most digestive enzymes are present, although amylase activity does not appear until the neonatal period.
263
What results from the digestion of cells and protein in amniotic fluid?
The digestion leads to the formation of meconium, which is fetal feces that may appear in the amniotic fluid due to increased maturity or fetal stress.
264
When do functional renal corpuscles first appear in the developing fetus?
Functional renal corpuscles first appear at 22 weeks gestation, and filtration begins at this time.
265
How does glomerular filtration change as the fetus approaches term?
Glomerular filtration increases towards term as the number of glomeruli increases and fetal blood pressure rises.
266
What significant contribution does fetal urine make during pregnancy?
Fetal urine makes a significant contribution to amniotic fluid.
267
When can the external ear be visualized in the developing fetus?
The external ear can be visualized from 10 weeks onwards.
268
When are the middle ear and ossicles fully formed?
The middle ear and the three ossicles are fully formed by 18 weeks gestation.
269
When does the inner ear reach full development, and what sensory ability does this confer?
The inner ear is fully developed by 24 weeks gestation, allowing for sound perception.
270
How is visual perception in the fetus assessed, and what developments occur late in pregnancy?
Visual perception is difficult to assess, but some light perception through the maternal abdominal wall likely develops in late pregnancy, and fetal eye movements can be observed.
271
7. When does the amniotic sac begin to develop during pregnancy?
The amniotic sac develops as early as 7 days after conception.
272
What is the significance of the inner cell mass in the blastocyst regarding amniotic fluid?
The first signs of the development of the amniotic cavity can be seen in the inner cell mass of the blastocyst.
273
Up to what gestational week is there significant water transfer across fetal skin before keratinization begins?
Significant water transfer may occur by transudation across the fetal skin up to 24 weeks gestation when keratinization begins.
274
What contributes significantly to amniotic fluid volume in the second half of pregnancy?
In the second half of pregnancy, fetal urine provides a significant contribution to amniotic fluid volume.
275
What condition is associated with renal agenesis and minimal amniotic fluid volume?
Oligohydramnios is the condition associated with renal agenesis, characterized by minimal amniotic fluid volume.
276
How often is the total volume of water in the amniotic sac turned over?
The total volume of water in the amniotic sac is turned over every 2–3 hours.
277
What condition is known as polyhydramnios, and what causes it?
Polyhydramnios is characterized by excessive amniotic fluid volume and is commonly associated with congenital abnormalities that impair the ability to ingest amniotic fluid.
278
What is vernix, and when does it cover the fetus's skin?
Vernix is a milky-white, lipid-rich substance made of fetal dermal cells and sebaceous gland secretions that covers the fetus's skin during the 3rd trimester.
279
What is the estimated volume of amniotic fluid by 8 weeks gestation?
By 8 weeks gestation, approximately 5–10 mL of amniotic fluid has accumulated.
280
When does the maximum volume of amniotic fluid occur, and what is that volume?
The maximum volume of amniotic fluid occurs at 38 weeks gestation, reaching about 1000 mL.
281
What happens to amniotic fluid volume by 42 weeks gestation?
By 42 weeks gestation, the volume of amniotic fluid may fall below 300 mL.
282
Why is the estimation of amniotic fluid volume important during pregnancy?
The estimation of amniotic fluid volume forms a standard part of the ultrasound assessment of fetal wellbeing.
283
Clinical significance of amniotic fluid volume
284
What is the most common anomaly associated with hydramnios?
The most common anomaly associated with hydramnios is anencephaly.
285
List some anomalies associated with hydramnios in order of frequency.
1. Anencephaly
2. Oesophageal atresia
3. Duodenal atresia
4. Iniencephaly
5. Hydrocephaly
6. Diaphragmatic hernia
7. Chorioangioma of the placenta
286
What are some complications associated with hydramnios?
Complications of hydramnios include:
Unstable lie
Cord prolapse or limb prolapse
Placental abruption due to sudden release of amniotic fluid
Postpartum hemorrhage from over-distension of the uterus
Maternal discomfort and dyspnea
287
What is the procedure for amniocentesis?
Amniocentesis involves inserting a fine-gauge needle through the anterior abdominal wall under aseptic conditions and local anesthesia to obtain amniotic fluid.
288
When is amniocentesis typically performed during pregnancy?
Amniocentesis is commonly performed at 14–16 weeks gestation but can be done as early as 12 weeks in some circumstances.
289
Why is ultrasound guidance important during amniocentesis?
Ultrasound guidance is important to identify the best and most accessible pool of amniotic fluid and to avoid the placenta and fetus during the procedure.
290
What is checked before and after performing amniocentesis?
The presence of a fetal heartbeat is checked both before and after the procedure.
291
What are the indications for amniocentesis?
Indications for amniocentesis include:
Chromosomal abnormalities and sex-linked diseases
Metabolic disorders
Estimation of fetal lung maturity
292
How can amniocentesis be used to diagnose chromosomal abnormalities?
Amniocentesis allows for the culture of fetal cells to determine the fetal karyotype, revealing chromosome abnormalities such as those in Down’s syndrome and Turner’s syndrome.
293
What is the significance of estimating fetal lung maturity using amniotic fluid?
Estimating the lecithin/sphingomyelin ratio in amniotic fluid helps assess functional lung maturity after 28 weeks gestation and before premature delivery, aiding in the management of respiratory distress syndrome.
294
What is commonly administered to pregnant women to treat the risk of respiratory distress syndrome?
Corticosteroids are routinely administered to help manage the risk of respiratory distress syndrome.
295
8. Define "live birth" according to ICD-10.
A live birth is the complete expulsion or extraction from its mother of a product of conception, which, after separation, breathes or shows any other evidence of life (e.g., heartbeat, umbilical cord pulsation, or voluntary muscle movement), regardless of the pregnancy duration.
296
What is the definition of stillbirth or fetal death?
Stillbirth or fetal death is defined as death prior to the complete expulsion or extraction from the mother, indicated by the absence of breathing or any evidence of life after separation.
297
What does the perinatal period encompass?
The perinatal period begins at 22 completed weeks (154 days) of gestation and ends seven completed days after birth.
298
Differentiate between early neonatal deaths and late neonatal deaths.
Early neonatal deaths: Occur during the first seven days of life (0–6 days).
Late neonatal deaths: Occur after the seventh day but before the 28th day of life (7–27 days).
299
What is the perinatal mortality rate (PNMR)?
The perinatal mortality rate (PNMR) is the number of stillbirths and early neonatal deaths per 1000 total births (including live births and stillbirths).
300
How is the stillbirth rate (SBR) calculated?
The stillbirth rate (SBR) is calculated as the number of stillbirths per 1000 total births.
301
Define the neonatal mortality rate (NMR).
The neonatal mortality rate (NMR) is the number of neonatal deaths occurring within the first 28 days of life.
302
What factors have contributed to the decline in PNMR in developed countries?
Factors contributing to the decline in PNMR include:
Improved quality of obstetric and neonatal care
Improved socioeconomic conditions
Active screening programs for congenital abnormalities
303
How does maternal age affect perinatal mortality rates?
Maternal age affects perinatal mortality rates as follows:
Mothers under 20 years are 1.3 times more likely to have stillbirths or neonatal deaths.
Mothers over 40 years are 1.8 times more likely compared to mothers aged 25–29 years.
304
What impact does socioeconomic status have on perinatal mortality?
Mothers in the most deprived areas are 1.7 times more likely to have a stillbirth and 2.1 times more likely to experience a neonatal death compared to mothers in the least deprived areas.
305
What percentage of mothers with stillbirths and neonatal deaths smoked compared to the general population?
Stillbirths: 22% of mothers smoked.
Neonatal deaths: 23% of mothers smoked.
Compared to 15% of women in the general population.
306
What is the largest contributor to perinatal mortality?
Stillbirths are the largest contributor to perinatal mortality.
307
What are the limitations of traditional classification systems for stillbirth causes?
Traditional classification systems, like the Wigglesworth and Aberdeen classifications, often report up to two-thirds of stillbirths as having unexplained causes.
308
What does the ReCoDe system classify?
The ReCoDe (Relevant Condition at Death) system classifies the relevant condition present at the time of death, identifying causes of stillbirth.
309
What was identified as the most common cause of stillbirth using the ReCoDe system?
Using the ReCoDe system, fetal growth restriction was identified as the most common cause of stillbirth, accounting for 43% of cases, while only 15.2% remained unexplained.
310
What new classification was introduced by CMACE in the 2008 Perinatal Mortality report?
The CMACE classification introduced in the 2008 Perinatal Mortality report emphasized placental pathology to identify patterns in causes of death and preventable causes, focusing on:
Antepartum or intrapartum hemorrhage
Intrauterine growth restriction (IUGR)
Specific placental conditions
311
What percentage of stillbirths are intrapartum stillbirths in developed countries?
In developed countries, intrapartum stillbirths represent approximately 10% of estimated stillbirths.
312
What is the estimated rate of intrapartum stillbirths in developing regions?
In developing regions, the average rate of intrapartum stillbirths is estimated at 9 per 1000 births occurring during delivery.
313
What are the primary causes of intrapartum deaths?
Complications of childbirth are the cause of almost all intrapartum deaths, and these complications are largely avoidable.
314
What are the major global causes of neonatal deaths?
The major causes of neonatal deaths globally include:
Congenital anomalies
Prematurity
Birth trauma
Infections
315
What are the primary causes of early neonatal deaths?
Early neonatal deaths are mostly due to complications during:
Pregnancy or childbirth
Preterm birth
Malformations
316
What causes late neonatal deaths?
Late neonatal deaths are primarily caused by:
Neonatal tetanus
Infections acquired either at home or in hospitals
317
When do most deaths from neonatal tetanus occur?
Most deaths from neonatal tetanus occur between the 7th and 10th day of life.
318
What association does low birth weight have with neonatal deaths?
Low birth weight is not a direct cause of neonatal death but is an important association. Approximately 15% of newborns weigh less than 2500 g, with rates ranging from 6% in developed countries to over 30% in poorly developed countries.
319
What are some of the major causes of neonatal deaths?
The major causes of neonatal deaths include:
Respiratory disorders
Major congenital anomalies
Neurological disorders
