Parturition Flashcards
progesterone
progesterone block and uterine quiescence
cervical closure
luteal and placental sources
estrogens
produced during pregnancy, can silence estrogen
progesterone profiles
fall at parturition- bitch, queen, sow
some peak towards parturition prior to rapid decline= woman, mare, cow and ewe
woman endocrine profile
E2 and P4 run together and rapid decline as hit parturition
Ewe endocrine profile
P4= gradual rise throughout and fall at parturition
E2 peaks right before parturition and falls at parturition
Sow endocrine profile
At ovulation= peak of P4
E2 peaks as approaches parturition
Mare endocrine profile
P4= birise and declines as estrogen increases prior to estrogen decline at parturition
Cow endocrine profile
P4 high at ovulation and then decreases, remains steady throughout before a steady incline and drop at parturition
estrogen has an increase prior to parturition
progesterone
pro gestational
estrogen
increased uterine responsiveness
PGF2a
luteolysis and contractions
oxytocin
contractions
relaxin
genital tract softening
parturition concept
must be timed to match degree of fetal maturation with the ability of the fetus to survive outside the uterus
once initiated the process of parturition is difficult to interrupt or delay
the liggins contribution
fetuses control parturition timing
hypophysectomy= pituitary gland removal or adrenalectomy prevents parturition
infusion of ACTH or cortisol induces premature parturition and visceral maturation
women with preterm labor treated with glucocorticoid
critical observation in experiments
fetal sheep exposed to agent have a malformation that is characterized by delay in parturition
Fetal Hypothalamic-pituitary-adrenal (HPA) axis
activation/maturation of the fetal HPA axis results in increase in fetal corticotropin releasing hormone (CRF/CRH), ACTH and cortisol
fetal stress= hypoxia, overcrowding, nutritional concern
Fetal HPA
hypothalamus (CRF) to ant. pituitary (ACTH) to adrenal cortex (cortisol)
fetal cortisol
induces enzymatic changes in placenta, communicates with the dam
promotes prostaglandin synthesis
instrumental in fetal maturation (ex:lungs)
fetal cortisol released= useful because causes lung to mature so have surfactant
Sheep
decrease progesterone and increase estrogen which causes more irritation, gravid uterus and cervix softening
enzymatic pathway
fetal cortisol induces
progesterone to estradiol via enzymatic conversion in the placenta
progesterone falls and estrogen rises
aromatase changes by taking away number of carbons
progesterone falls
- enzymatic- fetal cortisol induces placental conversion of progesterone to estrogen
- luteolysis- PGF2a, importance in CL dependent species
removal of progesterone block
estrogen rises
because progesterone decline
enzymatic- fetal cortisol induces placental conversion of progesterone to estrogen
increases uterine sensitivity to oxytocin, increased lubrication and softening, promotes release of PGF2a
relaxin
encourages pelvic, genital tract and cervical softening to facilitate parturition
externally assessed as parturition nears: vulva, perineum and pelvic ligaments soften and relax
prostaglandin
PGF2a release will cause luteolysis if the CL still present
PGF2a will cause uterine (myometrial) contractions- smooth m.
oxytocin
will cause myometrial contractions
very high at parturition
uterine contractions can subsequently promote more oxytocin and PGF2a release
Ferguson reflex
Ferguson reflex
neuroendocrine reflex dissension of the cervix and vagina causes release of oxytocin from the posterior pituitary uterine contractions result further dissension occurs more oxytocin released- lots of feedback
process triggered by fetal stress
increase in fetal ACTH, fetal cortisol released
Fetal cortisol
increases PGF2a release- triggering relaxin (pelvic ligament stretching) and luteolysis along with increased myometrial contractions
can trigger enzymes that convert P4 to E2 which causes increased myometrial contractions and increased secretion by female tract allowing lubrication
increased myometrial contractions
increase pressure, increase cervical stimulation, increase oxytocin, maximum pressure
Thorburn hypothesis
prostaglandin E2 injections into fetuses IV increases ACTH secretion
PGE2 secreted from ovine placenta= hormonal signal which stimulates fetal ACTH secretion at the end of gestation
PGF2a vs. PGE2
OH vs. double bond O
3 stages of parturition
preparation, fetal expulsion with true labor, expulsion of the fetal membranes
Stage I
preparation
cervical dilation, myometrial contractions, some fetal positioning
Stage II
fetal expulsion with true labor
myometrial and abdominal contractions (generally obvious)
Stage III
expulsion of the fetal membranes
species variability in length of each stage
Bovine- cow= slow, Heifer= even slower
horse= fast explosive
forceful contractions
uterine myometrial (smooth m.) contractions
abdominal contractions
calcium necessary
Horse stage I
preparation
relaxed tail head, soft perineal tissues, sweating, colicky, nervous
Stage II horse
begins with chorioallantois rupture, explosive in mare
water breaks, amnion visible and fetal expulsion completed
stage III horse
placental expulsion
bovine parturition
stage I= preparation
isolated from herd, udder= colostrum and edema, tissue softening
Stage III in cows
mechanism of fetal membrane passage
continued myometrial contractions
vasoconstriction and inflammation
problem if retain fetal membranes
Puerperium
time from fetal delivery until complete uterine involution
involution varies by species:
cow-about month to 1.5 months
mare- about 2 weeks
bitch- about 2 months and more
Uterine involution
gross appearance of uterus- dramatic decrease in uterine size, fetal membrane expulsion, evacuation of fluids remaining in uterus
histological appearance of uterus= tissue healing
clearance of bacterial contamination from act of parturition
Lochia
normal postpartum debris and fluids which are passed out through the vagina and vulva
length of time of discharge varies among species
minimal odor
clinical relevance
assisted delivery for dystocia
therapy for retention of fetal membranes
general parturition
Fetal HPA activation, decreased progesterone, increased estrogen, increased oxytocin and PGF2a, relative uterine quiescence changes to dramatic uterine activation
