Theory 1 Flashcards
(81 cards)
1
Q
Growth refers to the increasing size of the fetus and occurs throughout normal pregnancy. It is a result of two factors
A
- an increase in the number of fetal cells
- growth in the size of the fetal cells.
2
Q
Development refers to the functional and structural changes that occur in the fetal organ systems and occur throughout normal pregnancy. Development is more complex than growth and includes:
A
- the differentiation of the cells and tissues
- the organization of cells and tissues into organ systems
- cell growth.
3
Q
Define Appropriateness for gestational age
A
refers to the relationship between fetal growth (size) and development (gestational age). It is an important factor in assessing the health of a fetus, or of a newborn, and we will look at this in more detail when discussing fetal assessments.
4
Q
Define Preterm or premature:
A
born before completion of 37 weeks of gestation.
5
Q
define Late preterm:
A
born between 34 weeks and 37 weeks of gestation. This group if the fastest growing subset of preterm infants; they account for 74% of all preterm births” (Shaw, 2008)
6
Q
define Term:
A
born between the beginning of week 38 and the end of week 42 of gestation.
7
Q
define Post-term (postdate)
A
born after the completion of week 42 of gestation.
8
Q
define Postmature:
A
born after the completion of week 42 gestation and showing the effects of progressive placental insufficiency.
9
Q
First trimester
A
weeks 1-13
10
Q
Second trimester:
A
weeks 14-26
11
Q
Third trimester:
A
weeks 27-40
12
Q
define cephalocaudal pattern
A
This means an embryo-fetus develops and matures from head towards extremities. Fetal growth and development is extremely rapid during the first 18 weeks after conception
13
Q
define organogenesis
A
is when a fetus’ organs and structures are formed and begin to function. The fetal brain, in particular, undergoes extremely rapid growth and development during this early period, and uses a considerable amount of the total nutrients available to the embryo-fetus.
14
Q
summerize development of fetus after 18 weeks (last 20-22 weeks of pregnancy) including weights
A
a fetus focuses more on growth than development. Fetal weight goes from approximately 400 grams at 18 weeks to an average of 3400 grams at birth. This represents an average weight gain of 120–220 grams a week, or 20–30 grams (around one ounce) a day. Fetal organs and structures do continue to develop, becoming more sophisticated and refined in their function, in preparation for life outside a woman’s womb.
15
Q
define preconception
A
begins on the first day of a woman’s menstrual cycle and lasts until conception occurs.
this is the ripening of the egg or ovum and uterus lining grows thicker to recieve the fertilized egg.
16
Q
Define conception
A
Conception, which marks the real beginning of pregnancy for most of us, occurs when one of these sperm finds and penetrates the mature egg.
17
Q
describe pre-embryonic stage
A
fetal age: 0-2 wks
egg differentiates into different specialised cells, travels down fallopian tube and implants into the uterus
18
Q
describe embryonic stage
A
fetal age: 2-8 wks
when embryo becomes a fetus
rapid growth and development organogenesis occurs.
Heart beats :)
head is disproportionately large due to rapid brain development
arms and legs have joints
19
Q
describe fetal stage
A
9 wks to term
starts at the begining of 9th week.
week 14, placenta is fully formed
20
Q
when is the placenta fully formed?
A
14 weeks
21
Q
the placenta is the only organ the contains cells from two different individuals: Fetus and mother
T or F
A
True!
22
Q
what maternal component forms the placenta?
A
The Decidua basalis:
endometrium or uterine lining under the site of implantation
23
Q
what fetal component forms the placenta?
A
from the chorionic sac: develops branches of villas that penetrate the decidua basalis
24
Q
What is the role of the placenta?
A
acts as life support continuous O2 nutrients removes carbon dioxide produces hormones that maintain pregancy, facillitates fetal development and prepares mothers body for lactation
25
is there mixing of blood from mom to babe via placenta?
NO.
It is important to understand that the fetal/maternal exchange (of gases, nutrients, and wastes) occurs across or through the cell membranes that line the outside of the chorionic villi unless there is a break in these membranes, there is no mixing of maternal and fetal blood. The baby can, therefore, have a completely different blood type from the mother
26
can substances pass through the placenta?
YES
Although blood cannot pass through these cell membranes, many substances can, including most drugs, many infectious agents, and maternal antibodies. The placenta is not a “barrier,” but a sieve.
27
what hormones does the placenta secrete?
steroids:
estrogen and progesterone
```
protein:
human chronic gonadotropin (hCG)
chronis somatomsmmotropin (or) human placental lactogen (hPL)
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28
list the metabolic functions of the placenta
respiration
nutrition
excretion
and storage
29
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placenta
30
what makes up the umbelical cord?
one vein - transports O2 and nutrients
| two arteries - transport carbon dioxide and wastes from fetus
31
what is Whartons jelly?
gelatinous substance that surrounds the umbellical vein and arteries
prevents the compression of vessels
32
How many fetal membranes are surrounding the fetus? what is their names?
there are 2
Chorion - develops first chornic villi burrow into the decidua to become the fetal portion of the placenta
amnion - develops fromt he ectoderm. layer lies closes to the embryo forming a fluid like sac. the amnion will grow until it comes into contact with the chorion
eventually the two membranes adhere to form the bag of waters or fetal sac that contains the AMNIOTIC FLUID
33
when do fetal kidneys start to function?
10 - 12 weeks
34
how much amniotic fluid can develop during pregnancy?
800-1200 cc
35
define oligohydramnios
amniotic fluids measuring less than 300 cc in the third trimester. indicates renal abnormalities
36
define polyhydramnios
amniotic fluid measuring 2L or more. associated with gastrointestinal anomalies
37
describe amniotic fluid
clear, pale straw coloured
characteristic odor neither foul smelling or like urine
composed mostly of H2O
38
functions of amniotic fluid?
- helps to maintain a constant TEMPERATURE for the embryo/fetus.
- equalizes pressure and CUSHIONS fetus from trauma.
- protects the embryo/fetus from INFECTION.
- distends the amniotic sac, allowing freedom of MOVEMENT for the fetus.
- keeps the embryo from becoming tangled with the membranes.
- provides fluid for the fetus to swallow and “BREATHE”
- provides a repository for fetal wastes (urine).
- in labor, as long as the membranes remain intact, protects placenta, umbilical cord, and baby from pressure of contractions and aids in the effacement and dilation of the cervix
39
if a womens blood circulation is compromised, what is the best position to ensure maximum blood flow to the placenta?
lying on LEFT side
40
list 5 key features of fetal circulation.
- fetal oxygen needs are relatively low
- the placenta is the organ of gas exchange
- the fetal lungs are collapsed and fluid filled
- the fetal brain and heart have the highest oxygen needs.
- right-to-left shunting occurs through the ductus arteriosus and foramen ovale.
41
Fetal oxygen needs are relatively low.
The fetus has low oxygen needs because many oxygen using activities such as respiration, thermoregulation, and digestion are carried out in the maternal system. The fetal arterial pO2 is approximately 30. This is known as relative hypoxemia, which means that although 30 would be indicative of tissue hypoxia in extrauterine conditions, because of the low oxygen needs of the fetus in utero, there is no fetal tissue hypoxia. The low fetal pO2 causes pulmonary vasoconstriction, which serves to keep the lungs hypoperfused. The low fetal pO2 is also responsible for keeping the ductus arteriosus patent.
42
The placenta is the organ of gas exchange.
Therefore blood must flow from the fetus to the placenta and from the placenta to the fetus. The umbilical arteries and veins accomplish this. The umbilical arteries carry deoxygenated blood to the placenta; the umbilical vein carries oxygenated blood to the fetus. The placenta is a low pressure organ; it offers very little resistance to blood flow. This contributes to the fetus’ low systemic blood pressure and low left ventricular pressure.
43
The fetal lungs are hypoperfused and fluid filled.
They are not the organ of gas exchange. Rather, they are growing and developing and in order to do this they require a small amount of oxygen and nutrients. Therefore only about 10% of the fetal cardiac output perfuses the lungs. The fetal lungs are, as a result, hypoperfused. The fetal lungs are a high pressure system; meaning they offer high resistance to blood flow. This is because the pulmonary arterioles are vasoconstricted. This vasoconstriction is due to the low fetal pO2. Because gas exchange does not occur in fetal circulation, the alveoli are filled with fluid, rather than with air. It is generally agreed that fetal lung volumes are less than neonatal lung volumes and that newborn lungs must expand immediately after birth.
44
The fetal brain and heart have the highest oxygen needs.
Both of these organs have high oxygen requirements. Because the fetal pO2 is relatively low (owing to the low oxygen needs of other organs), fetal circulation functions in such a way as to divert the blood with the highest oxygen content to the brain and heart. This is accomplished via the ductus arteriosus and the foramen ovale.
45
Right-to-left shunting occurs through the foramen ovale and ductus arteriosus
Oxygenated blood enters fetal circulation via the ductus venosus and the inferior vena cava, into the right atrium. High pulmonary pressure diverts blood away from the lungs through the foramen ovale into the low pressure left atrium. From there, oxygenated blood enters the left ventricle and immediately perfuses the heart (coronary artery) and brain (carotid arteries).
46
explain what is meant by the expression "the fetus exists in a state of relative hypoxemia"
“The fetus exists in a state of relative hypoxemia” refers to the low fetal pO2 , which, at 30, would cause tissue hypoxia in extrauterine life. However, in utero, fetal oxygen needs are low, meaning that the pO2 of 30 is sufficient to meet the fetal tissue oxygen needs. Therefore, the fetus does not suffer tissue hypoxia. Fetal oxygen needs are low because the maternal system is conducting many oxygen using functions such as metabolism, digestion, thermoregulation. In addition, ventilation, which uses a great deal of energy and oxygen, is not occurring in the fetus. Remember that the lungs are collapsed, fluid filled, and not functioning.
47
what effects of the low fetal PO2 have on the pulmonary vessels and the ductus arterioles
The fetal pO2 of 30 results in pulmonary vasoconstriction3 and causes dilation of the ductus arteriosus.
3Pulmonary vasoconstriction leads to increased pulmonary vascular resistance, high pulmonary artery pressure, righttoleft shunting, and pulmonary hypoperfusion.
48
The pressure gradients which exist betweent he right and left side of the fetal heart play a significant tole in fetal circulation. determine which side of the heart is pumping against pressure
The right ventricle — because it is pumping blood to collapsed, fluid-filled, vasoconstricted lungs — is experiencing higher pressure than the left ventricle which is pumping blood to the low pressure placenta
49
explain the direction of blood flow through the foremen ovale and the ductus arterioles
Blood will flow through both the foramen ovale and the ductus arteriosus in a right-to-left direction. Blood always flows along the path of least resistance. In the fetus there is high pressure on the right side of the heart and low pressure on the left, making the path of least resistance from right to left. At the foramen ovale blood flows from the right atrium to the left atrium. At the ductus arteriosus blood flows from the pulmonary artery into the aorta.
50
explain hoe the pressure gradient and the direction of flow through the foramen ovale and the ductus artiriosis would enable the brain and heart to recieve the most well oxygenated blood in the fetal circulation. (hint oxygenated blood arrives in the RIGHT atrium from the inferior vena cava and umbelical vein
As soon as you have red, oxygenated blood entering the aorta that blood is available to the heart and brain because the coronary and carotid arteries are the first arteries to arise from the aorta. The foramen ovale gets well-oxygenated blood from the right atrium into the left atrium. From there this blood enters the left ventricle and then into the aorta.
Deoxygenated blood returns to the right heart from the head (via the superior vena cava), enters the right atrium, then the right ventricle, and then enters the pulmonary artery. This blood encounters the ductus arteriosus and shunts into the aorta, thereby deoxygenating the blood in the portion of the aorta below the ductus arteriosus. Fortunately the ductus arteriosus is situated below the carotid and coronary arteries, permitting the carotids and coronaries to avoid receiving this deoxygenated blood. They have already received well-oxygenated blood from the ascending aorta. In this way, the ductus arteriosus shunts blood into the aorta in order to bypass the lungs and deliver blood to the less vital organs (gut, liver, kidney, legs) and the placenta. It is situated in such a way that the heart and head do not receive any of this deoxygenated blood.
51
when does "transition" begin
when the cord is cut and the infant takes her first breath
52
list the chain of events of transition
1) arterial po2 rises
2) pressure gradient changes
3) fetal shuts close
4) Lungs assume ther respiratory functions
53
what effect does the increasing NB po2 have on cardiovascular adaptation?
low fetal pO2 had on fetal circulation. You should be able to determine that the low fetal pO2 caused pulmonary vasoconstriction leading to hypoperfusion. Therefore the rising newborn pO2 will lead to pulmonary vasodilation and permit more blood to go to the lungs. (This is a good thing!) The low fetal pO2 also caused the ductus arteriosus to dilate, thereby staying patent and allowing shunting of deoxygenated blood from the pulmonary artery to the aorta, bypassing the lungs. Therefore a rising newborn pO2 will lead to ductal constriction and eventual closure. (This is a good thing too, because it stops the lungs from being bypassed.)
A rising pO2 is critical to successful transition. If the pO2 does not rise the pulmonary vessels will remain vasoconstricted, the ductus arteriosus will remain patent, right-to-left shunting will occur, and blood will bypass the lungs. If blood does not get to the lungs the pO2 will remain low and the infant will remain in a persistent state of fetal circulation. Without the placenta, this is not good. Some of you have likely already encountered this.
54
perinatal asphyxia can lead to a chain of events beginning with hypoxia and potentially ending with persistence of fetal circulation. describe the chain of events
more blood flow to heart & Brain
less blood flow to the other organs
metabolic acidosis is caused by anaerobic metabolism
combo of hypoxia and acidosis cause both cardiac and resp depression
infant born after experiencing perinatal hypoxia will be depressed with low apgar score,
55
fetal heart starts to beat (Primative)
3 weeks
56
beating heart seen on ultrasound
8 weeks
57
when can fetal heart rate be picked up on doppler
15-20 weeks
58
normal range of FHR
100-160 BPM
59
when is estimated gestational age of fetus calculated?
| aka nageles rule
number of weeks from the last menstral cycle
60
how do you calculate Nageles rule?
Last mentral period (LMP): date
+ 7 days
+ 9 months
= estimated date of delivery (EDD)
61
womens fundal height should correspond with approximate number of weeks she is pregnant at what stage? (symphysis fundal height) SFH
from 20 weeks
| SFH is 32 cm she is approx 32 weeks preggers
62
define AGA
is the term used to describe an infant whose weight is appropriate for the gestational age.
63
define SGA
is the term used to describe infants who are small for gestational age. The weights of these infants fall below the tenth percentile.
64
define LGA
refers to infants who are large for gestational age. The weights of these infants are above the ninetieth percentile.
65
Cytomegalovirus (CMV)
this virus can be contracted from secretions and sexual contact and is often asymptomatic. It is one of the more common infections that cause birth defects such as mental retardation and loss of vision and hearing. It is estimated that 5-6% of women become infected and about 3% of their newborns have CMV infection (Sherwen, et al., 1999). Women who are routinely around young children have an increased risk of contacting this virus. Prevention of infection is recommended by good hand washing techniques, particularly after dealing with body secretions, and not sharing eating and drinking utensils. All women not in monogamous relationships are strongly encouraged to use latex condoms during intercourse.
66
Hepatitis Virus
hepatitis B is yet another virus that can be transmitted across the placenta, resulting in a high risk of fetal and neonatal hepatitis. Routine pregnancy testing includes a Hepatitis B screening. Neonates born to mothers who are Hepatitis B positive are given immunoglobulin at birth.
67
Human Immunodeficiency Virus (HIV)
worldwide, this presents one of the biggest threats to infants. Although not associated specifically with birth defects, the risk of mother to child transmission is anywhere from 15 to 40% in the absence of antiretroviral drugs (WHO, 1999, p. 5). In Canada HIV testing is recommended as part of pregnancy screening tests and is offered to all pregnant women. In 2005 the Public Health Agency of Canada reported that the proportion of infants confirmed to be HIV infected in Canada was 4%.
68
Rubella
when maternal to child transmission occurs in the first trimester there is a high rate of birth defects. Maternal rubella contact and fetal defects decrease rapidly as pregnancy progresses. Immunization against the rubella virus is recommended for all women of childbearing age. It is also recommended that any woman planning a pregnancy should wait three months after immunization before attempting to become pregnant. Rubella antibody titre testing is offered to all pregnant women whose preconception rubella status is unknown.
69
Syphilis Virus
this sexually transmitted virus can result in spontaneous abortion and if the pregnancy survives can cause serious deformities in a growing fetus. All pregnant women are offered a screening test for this virus which can be present asymptomatically.
70
Toxoplasmosis
this parasite is transmitted by contact with raw or undercooked pork and through contact with cat feces. All pregnant women are advised to avoid exposure by using gloves and hand washing after cleaning up kitty litters. There is a 25% chance of maternal-fetal transmission, resulting in prematurity, low birth weight, enlarged liver and spleen, visual defects, mental retardation, and cranial calcifications.
71
Varicella (Chicken Pox)
during the first trimester this virus has a 20% chance of causing fetal deformities. Risk after the critical period falls rapidly (Sherwen et al., 1999). If immune status to the varicella virus is unknown, the pregnant woman can be tested for antibodies. A varicella-zoster immune globulin is offered if a woman is not immune to varicella.
72
list drugs that have teratogenic effects
```
anticonvulsants
antibiotics
psychotropic drugs (no conclusive data for SSRI)
accutane
asprin
ibprophen
illicit drugs
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73
define hypoplastic growth restriction
| is is symmetrical or asymmetrical?
occurs early in gestation and results in decreased number of cells. It is associated with congenital anomalies due to the early onset of the insult: the growth problem is occurring at a time when organ systems are undergoing major structural development. Hypoplastic intrauterine growth restriction often results in arrested brain growth and small head size. Because these infants have both small bodies and small heads, the result is referred to as symmetrical growth restriction.
74
define Hypotrophic:
| is is symmertrical or asymmetrical?
occurs later in gestation and results in decreased size of fetal cells but not in decreased numbers. These infants do not generally have congenital anomalies and their heads often appear large for their bodies. This is because the insult causing decreased growth occurs late enough that head growth is not affected. These infants are said to have asymmetrical growth restriction.
75
common maternal causes for SGA
- pregnancy induced hypertension (decreased blood flow to fetus)
- severe maternal diabetes with vascular impairment (vascualr impairment causes decreased blood flow to fetus)
- maternal malnutrition
- maternal drug use (decreased blood flow to fetus)
76
common intrauterine causes of SGA
- placenta previa 9placenta too close to cervix)
- small placenta
- teratogens such as viral infections
77
list the factors that place preterm infants are risk for hypothermia
- immature CNS - immature tempurature regularion
- less brown fat
- less insulating subcutaneous tissue
- fewer nutrient stores
- decreased ability to shiver
- decreased ability to vasoconstrict
- limited ability to assume flexed position
- thinner skin
- larger surface area to body mass
78
fluid and electrolyte balance in preterm infants is different than older infants list as many differences you can:
- increased total body water (80–85% of body weight).
- increased extracellular water.
- immature renal function.
- high insensible (evaporative) water losses due to skin immaturity.
- high insensible water losses due to higher - - body surface area: body mass ratio.
79
protein, fat and carb absorption in both term and preterm infants is inefficient. what functional problems of the gestation tract contribute to the inefficient absorption of these essential nutrients?
Preterm gastrointestinal function is characterized by the following problems:
- inability to coordinate sucking, swallowing, and breathing
- weak or absent gag and cough reflexes
- incompetent cardiac sphincter leading to
gastroesophageal reflux
- delayed gastric emptying
- incompetent ileocecal valve
- impaired rectosphincteric reflex.
80
what causes placental insufficiency to occur after 36 weeks?
- previous history of placenta insufficiency
- diabetes
- high blood pressure
- high BMI
- multiple gestation
81
what problems are post term infants at risk for developing?
- asphyxia
- meccnium aspiration syndrome
- dysmaturity syndrome
- hypoglycemia
- polycythemia
- respiratory distress
