Pregnant and nursing patient Flashcards
(35 cards)
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What is the functions of the placenta?
- The placenta forms the functions of the kidneys and digestive and respiratory systems.
- Nutrients and O2 brought to the fetus in the maternal blood are acquired by the mother’s digestive and respiratory systems, and the CO2 and wastes transferred into the maternal blood are eliminated by the mother’s kidneys and lungs, respectively.
- The mother’s digestive tract, respiratory system, and kidneys serve the fetus’s needs as well as her own.
- The means by which materials move across the placenta depends on the substance.
- Many drugs, environmental pollutants, other chemical agents, and microorganisms in the mother’s bloodstream can also cross the placental barrier, and some of them may harm the developing fetus.
What does The placenta temporlariy become during pregnancy?
The placenta becomes a temporary endocrine organ during pregnancy.
During pregnancy three endocrine systems interact to support and enhance the growth and development of the fetus, to coordinate the timing of parturition (birth), and to prepare the mammary glands for nourishing the baby after birth. What are these 3 hormones?
- Placental hormones
- Maternal hormones
- Fetal hormones
Hormones secreted by the placenta play a critical role in maintaining pregnancy.
What are the most important hormones?
- Human chorionic gonadotropin (hCG)
- Estrogen
- Progesterone
Why is the placenta unique among endocrine tissues?
- Transient tissue
- Secretion of its hormones is not subject to extrinsic control. Instead, the type and rate of placental hormone secretion depend primarily on the stage of pregnancy.
What does the Human chorionic gonadotropin (hCG) do?
Peptide placental hormone that acts to prolong the life span of the corpus luteum (CL).
What does the corpus luteum do?
- CL of pregnancy is an ovarian endocrine unit that grows larger and produces increasingly greater amounts of estrogen and progesterone for ~10 weeks post-implantation.
- Maintenance of a normal pregnancy depends on high concentrations of estrogen and progesterone.
- Persistence of estrogen and progesterone maintains the thick, pulpy endometrial tissue and menstruation ceases during pregnancy.
What does a male fetus hCG stimulate?
hCG stimulates precursor Leydig cells in the fetal testes to secrete testosterone, which masculinises the developing reproductive tract.
Where is hCG eliminated?
hCG is eliminated in the urine.
What can hCG be an underlying trigger for?
hCG may be the underlying trigger for “morning” sickness
Why doesn’t the placenta secrete estrogen in the first place instead of secreting hCG, which in turn stimulates the corpus luteum to secrete this hormone (and progesterone)?
- The placenta does not have all the enzymes needed for estrogen synthesis in the first trimester.
- Estrogen synthesis requires a complex interaction between the placenta and the fetus.
When can the placenta synthesise progesterone? What is the amount of progesterone proportional to?
- The placenta can synthesise this hormone soon after implantation.
- However, the amount of progesterone produced is proportional to placental weight.
- The placenta is too small in the first 10 weeks to produce enough progesterone to maintain the endometrial tissue.
- The increase in circulating progesterone in the last 7 months of gestation reflects placental growth during this period.
What are the roles of estrogen and progesterone during pregnancy?
- High concentrations of both hormones are required to maintain pregnancy.
- Recall both hormones are secreted by the CL of pregnancy in the 1st trimester and by the placenta in the 2nd and 3rd trimesters.
What are the roles of estrogen during pregnancy?
- Stimulates growth of the myometrium, which increases in size throughout pregnancy. The stronger uterine musculature is needed to expel the fetus during labour.
- Also promotes development of mammary gland ducts, through which milk will be ejected during lactation.
What is the role of progesterone during pregnancy?
- Main role is to prevent miscarriage by supressing contractions of the uterine myometrium.
- Also promotes formation of a mucus plug in the cervical canal to prevent vaginal contaminants from reaching the fetus.
- Progesterone stimulates development of milk glands in the breasts in preparation for lactation.
What are the maternal body systems responses to the increased demands of gestation?
- The period of gestation (pregnancy) is ~38 weeks from conception.
- A number of physical changes within the mother accommodate the demands of pregnancy:
- Uterine enlargement
- Breasts enlarge and develop the ability to produce milk
- Volume of blood increases by 30%
- Weight gain (mostly from increased weight of the uterus and increased blood volume)
- Respiratory activity increases ~20%
- Urinary output increases, and the kidneys excrete additional wastes from the fetus
- Increased nutritional requirements for the mother
What does Parturition (labour, delivery or birth) require?
- Dilation of the cervical canal to accommodate passage of the fetus from the uterus through the vagina and to the outside and
- Contractions of the uterine myometrium that are strong enough to expel the fetus
What are some changes during late gestation prepare for parturition?
Braxton-Hicks contractions
- Occur during the last trimester
- Mild contractions that are experienced with increasing strength and frequency
- Sometimes regular enough to be mistaken for the onset of labour (“false labour”)
Softening of the cervix
- Dissociation of cervical collagen fibres allows cervix to dilate during labour
- Cervical softening is caused largely by relaxin, a peptide hormone produced by the CL of pregnancy and by the placenta
- (Relaxin also relaxes the birth canal by loosening the connective tissue between the pelvic bones)
The fetus shifts downwards (the baby “drops”)
- Normally orientated so that the head is in contact with the cervix
- In a breech birth, any part of the body other than the head approaches the birth canal first
What is the first stage of birth?
First stage: Cervical dilation
- At the onset of labour or sometime during the first stage, the membrane surrounding the amniotic sac ruptures. Amniotic fluid escapes out of the vagina and helps lubricate the birth canal.
- Cervix is forced to dilate to accommodate the diameter of the baby’s head (max. ~10 cm)
- May take many hours
