Flashcards in Gestational Physiology Deck (16)
When does beta-hCG secretion begin? What is its function?
- beta-hCG secretion begins about 6-7 days after fertilization (about day 8 after ovulation)
- it acts similarly to LH and mainly acts to keep the corpus luteum from degrading into the corpus albicans until the placenta can take over the endocrine function
When does the placenta take over the corpus luteum's role?
- the placenta starts to take over about 6 weeks in, completely replacing the corpus luteum by about week 10
What change in hormones does parturition require? What is the mechanism behind this? What changes in the cervix occur to prepare for parturition?
- parturition (delivery) requires a drop in progesterone (enough so that E is present in more amounts than P)
- normally, during pregnancy, progesterone decreases the uterus' sensitivity to contractile stimuli by inhibiting the expression of CAPs genes (CAPs: contraction associated proteins) such as oxytocin receptors and PG receptors
- estrogen stimulates CAPs expression
- cervix: softens and dilates (normally it is rigid and closed)
What is the main sex hormone of pregnancy? What is its normal value in pregnancy? Which value is associated with an 80% spontaneous abortion rate? Which value is associated with a nearly 100% rate?
- main sex hormone of pregnancy is progesterone (made by the corpus luteum and then by the placenta)
- normal pregnancy values: 10-35
- pregnancies with values less than 10 have an 80% abortion rate
- pregnancies with values less than 5 have a near 100% abortion rate
What are the four stages of parturition (0, 1, 2, and 3)? What hormones and factors are associated with each stage?
- parturition has 4 phases
- 0: quiescence; dominated by progesterone
- 1: activation and cervical ripening; progesterone lowers, estrogen increases, CRH increases
- 2: expulsion of fetus (this is when myometrial activity peaks); PGF2alpha and oxytocin
- 3: expulsion of placenta and uterine involution: oxytocin
What causes the increase in estrogen associated with triggering parturition?
- (note that the drop in progesterone is the major trigger for parturition, but raised levels of estrogen are also important)
- the raised E levels are actually due to increases in hypothalamic secretion of CRH that occurs during parturition
- the CRH stimulates adrenal cortical synthesis (via ACTH), resulting in increased androgen synthesis and subsequent conversion into estrogen
What two things does implantation require in order to occur? What are the four phases of implantation?
- implantation requires a blastocyte (requires trophoblastic cells) and a receptive endometrium (which is maintained by a high P:E ratio)
- (the receptive endometrium is known as a decidua; this process is called decidualization)
- 1) hatching (lysis/shedding of zona pellucida)
- 2) apposition (cell-to-cell contact)
- 3) adhesion
- 4) invasion (cytotrophoblastic processes flow in between the epithelial cells of the endometrium and digest them)
What is the embryonic period? What four things does the survival of the embryo depend on?
- embryonic period is the time from fertilization to week 8 of gestation
- embryonic survival requires a functional placenta, yolk sac, fetal liver, and CVS
What is the first fetal organ to develop (after the placenta)?
- the heart!
- the heart starts contracting around day 21
What is the greatest threat to a pre-term baby? What can we give to improve mortality?
- greatest threat to pre-term baby is pulmonary immaturity
- give corticosteroids and surfactant to these neonates to help decrease the chances of respiratory distress
- (the lungs are essentially developing throughout the entire length of gestation)
What is SGA? What percentile must the fetus be less than to fall into this classification? How is it related to IUGR? What is LGA? What percentile must the fetus be above to fall into this category?
- SGA: small for gestational age; fetus is less than the 10th percentile
- IUGR (intrauterine growth reduction) is the term used to small fetuses; severe IUGR can lead to SGA
- LGA: large for gestational age; fetus is greater than the 90th percentile
What are the symptoms of pregnancy? What are some symptoms that may indicate an underlying complication?
- normal symptoms of pregnancy: amenorrhea, breast tenderness, nausea/vomiting, fetal movements
- complication/disease: vaginal bleeding, abdominal pain, hyperemesis gravidarum
What tests/screenings do we run as a routine 1st antenatal screening? What do we screen for between weeks 11 and 14? How often should pregnant patients visit their doctor?
- 1st antenatal screening: FBC (check for anemia, platelet disorders), Rhesus factor status, serology (HIV, HBV, HCV, syphilis, rubella)
- between weeks 11 and 14, fetal aneuploidy screening can be done via nuchal translucency and other noninvasive prenatal tests
- patients should visit once every 4 weeks up to week 28, then once every 2 weeks up to week 36, and then every week until delivery
What is the puerperium period? What physiological changes occur during this period?
- this is the postpartum period
- it is usually defined as the period from delivery to 6 weeks after delivery
- the body returns to its pre-pregnant state during this period
What are common early maternal issues? What about more long-term issues?
- early: afterbirth pains, perineal discomfort, constipation/hemorrhoids, voiding, MSK pain, neuropathy, postpartum blues, breast engorgement
- longer-term: voiding, persistent back pain, sexual dysfunction