Parturition Flashcards
What happens when the fetal hypothalamic-pituitary-adrenal axis is activated?
Increase in Corticotropin Releasing Hormone (CRH), Adrenocorticotropin Hormone (ACTH), and Cortisol
Causes of fetal stress
Hypoxia, overcrowding, nutritional compromise (?)
Functions of fetal cortisol
Induces enzymatic changes in placenta
promotes prostaglandin synthesis
important in fetal maturation e.g. lung development
Enzymatic changes
Placental enzymes convert progesterone to estrogen
Progesterone falls, estrogen rises
How does progesterone fall?
Enzymatic change due to fetal cortisol or due to luteolysis
Function of increased estrogen
Increases uterine sensitivity to oxytocin
increases lubrication and softening
promotes release of PGF2alpha
Function of PGF2alpha
Luteolysis, myometrial contractions
Oxytocin
Causes myometrial contractions, which releases more oxytocin and PGF2alpha and causes even more contractions
Relaxin
Facilitates parturition by softening pelvis, genital tract, and cervix
Ferguson reflex
Neuroendocrine reflex
Distension of cervix and vagina cause oxytocin release, causing uterine contractions, which cause further distension and release more oxytocin ect…
PGE2
Hypothesized to signal fetal ACTH secretion at end of gestation
Three stages of parturition
Preparation, fetal expulsion, expulsion of fetal membranes
Stage I
“preparation,” cervical dilation, myometrial contractions, some fetal positioning
Stage II
Myometrial and abdominal contractions, fetal expulsion with “true labor”
Stage III
Expulsion of fetal membranes
