Pregnancy and Parturition Flashcards
What produces relaxin?
Corpus Luteum and the Placenta in response to hCG
What is the function of relaxin?
- Inhibits myometrial contractions
- Relaxes pelvic bones and ligaments and softens cervix
What is the function of prolactin?
Stimulates lactogenic apparatus during gestation
What inhibits the lactation from prolactin during pregnancy?
Significant lactation is inhibited by high levels of progesterone and estrogen
Where does cholesterol used for steroidogenesis by the placenta come from?
Maternal LDL. The placenta cannot make cholesterol very well.
What does the placenta do with maternal cholesterol?
Converts it to pregnenolone
What happens to pregnenolone made in the placenta?
It is transported to the fetus where is is converted to DHEA-S and then 16-OH DHEA-S
What happens to the 16-OH DHEA-S?
It is transported to the placenta and converted into estriol which is delivered to the mother
What is the only synthesis mechanism for estriol?
It can only be made from fetal liver precursors
What is the function of progesterone in pregnancy?
Sustains the fetus
Inhibits uterine contractions
Inhibits maternal immune response
What is the function of estrogen in pregnancy?
Growth of breast and myometrium
Works with relaxin to soften pelvic ligaments
Role in parturition
What happens when the progesterone:estrogen ratio increases?
Maintains uterine quiescence and sustains the fetus
What happens when the progesterone:estrogen ratio decreases?
Linked in the start of parturition
What is the function of progesterone in BCPs?
Inhibits LH secretion which will block the LH surge in ovulation
What is the function of estrogen in BCPs?
Inhibits FSH release which will stabilize the endometrium
What are the effects of pregnancy on the CV system?
Increased CO and flow to uterus
Increased BV in anticipation of hemorrhage
Overall decreased hematocrit
What are the effects of pregnancy on the respiratory system?
Increased tidal volume and alveolar ventilation
Respiratory alkalosis due to hyperventilation will be compensated by renal excretion of HCO3-
What are the effects of pregnancy on the GI system?
Decreased GI motility
Decreased LES tone so there is more reflux
What are the effects of pregnancy on the endocrine system?
HPG axis is suppressed
Increased lactotrophs and PRL secretion
What are the effects of pregnancy on metabolism?
1st Half: Anabolic state
2nd Half: Catabolic state with insulin resistance that occurs due to hPL stimulation to increase plasma glucose and FAs
What is parturition?
The initiation and maintenance of labor and uterine evacuation
What is the main factor triggering parturition?
Decrease in progesterone:estrogen ratio
What is the function of cortisol in parturition?
CRH peaks at labor with it influencing contractions
CRH potentiates contracture response to prostaglandins and oxytocin
What is the function of oxytocin in parturition?
OXY sensitivity increases throughout pregnancy and peaks before parturition and is released with increasing frequency as labor continues in a positive feedback loop.
OXY functions to increase smooth muscle contractions via GPCR -> Calmodulin
What increases the number of OXY receptors throughout pregnancy?
Estrogen
How do alpha adrenergics function in pregnancy?
Stimulates myometrial contraction
How do beta adrenergics function in pregnancy?
Inhibits myometrial contraction
What is the Ferguson reflex?
Dissension of the cervix will lead to OXY release which stimulates uterine contractions in a positive feedback loop
What is the Letdown reflex?
Response to an infant crying via circulation to the breast that will cause muscle contraction and milk letdown
How does neural input from the spinal cord affect PRL?
- Neural input inhibits DOPA release
- Neural input will inhibit POA release of GnRH as well
