Ex 3 - Parturition Flashcards
What is parturition?
The physiologic process involved in delivery of the fetus and fetal membranes
How can we predict parturition?
Lots of ways!
previous hx, breeding date/gestation length, LH surge date (dogs), behavioral changes (nesting, anxious/restless), monitors, alarms, relaxation around perineum/pelvis, vulva becomes edematous, mammary enlargement, ventral edema (cows, mares –> gravid uterus compresses lymphatics - can rupture prepubic tendon), leaking milk/colostrum, waxing of teat ends (mares)
How does the body “relax” for parturition?
Relaxation of the cervix + ligaments surrounding pelvic canal
What blocks contractions during pregnancy?
P4!
Near term, P4 declines and the ‘progesterone block’ is removed to allow uterine contractions
What fetal hormone stimulates parturition?
CORTISOL!
cortisol causes change in ratio of E2 (inc) to P4 (dec)
This change stimulates Prostaglandin release
What hormones is parturition driven by? (maternal)
Prostaglandins & Oxytocin
These stimulate myometrial contractions!
- PGFs secreted from placenta and endometrium
- Oxytocin receptor #s inc on myometrial cells
- Oxytocin is released from post pit as fetus contacts cervix (Ferguson Reflex)
- Oxytocin enhances PGF release –> magnifies uterine contractions
What is the Ferguson Reflex?
Fetus contacts cervix –> stimulates oxytocin release from post pit
What can induce premature labor?
ACTH or cortisol, or corticosteroids
*Caution when rx’ing for pregnant animals
When does labor typically happen?
At night –> quiet, less stressful for mom
*mom doesn’t have much control over labor timing, but stress can delay a bit
Parturition in CL dependent spp
Fetal cortisol initiates parturition –> placental E2 inc –> PGF release causes regression of maternal CL (luteolysis) –> labor begins as maternal P4 conc. decline
Parturition in litter bearing spp
Parturition is initiated by signals from entire litter –> one early maturing fetus cannot trigger labor alone
rapidly maturing fetuses may be favored
How many stages of labor are there?
3
Stage 1 - Initial contractions
onset, end, CS
Onset: initial uterine contractions and relaxation of cervix
End: rupture of chorioallantois/water breaks (LA) or full dilation of cervix (SA)
CS: anorexia, restlessness, nervousness, lying down/standing, discomfort or colic, patchy sweating (mare), inc RR (bitch), actively running or squirting milk
Stage 1 - Duration
bitch, cow, mare
Bitch: 6-12 hr
Cow: 2-6 hr
Mare: 1-4 hr
Longer in primiparous dams (1st time moms) and shorter in multiparous dams (veterans)
Stage 1 - fetal movements
Head and forelimbs extend
Body rotates into dorsal position
Stage 2 - Delivery of fetus
onset, end, CS
Onset: rupture of chorioallantois (water breaks)
End: delivery of fetus
CS: active straining, appearance of translucent membrane (amnion at vulva), birth of fetus
Stage 2 - Duration
cow, mare, bitch
Cow: 30-60 mins
Mare: 12-30 mins
Bitch: 6 hrs
Longer in primiparous dams
**Delay in delivery process increases risk of fetal/neonatal death
Stage 2 - single vs multiple fetuses
Single: contractions start at horn tips, while caudal portion is relaxed
Multiple: contractions begin just cranial to the caudal-most fetus –> forces it through birth canal; process repeated for next most caudal fetus
Stage 3 - passage of fetal membranes (Placental)
Onset, end
Onset: delivery of fetus
End: passage of membranes
Stage 3 - duration
mare, cow, bitch
mare: 15 min - 3 hrs
cow: 30 min - 8 hr
bitch: fetal membranes expelled irregularly b/w fetuses
(mom alternates between stage II and stage III as each fetus is delivered)
Dams of many species eat their placentas
- may cause colic or choke
How can we induce labor?
- ruminants
- CL dep spp
- horses
- corticosteroids
- prostaglandins
- oxytocin
