Ex 3 - Parturition

Question 1

What is parturition?

Answer 1

The physiologic process involved in delivery of the fetus and fetal membranes

Question 2

How can we predict parturition?

Answer 2

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)

Question 3

How does the body “relax” for parturition?

Answer 3

Relaxation of the cervix + ligaments surrounding pelvic canal

Question 4

What blocks contractions during pregnancy?

Answer 4

P4!

Near term, P4 declines and the ‘progesterone block’ is removed to allow uterine contractions

Question 5

What fetal hormone stimulates parturition?

Answer 5

CORTISOL!

cortisol causes change in ratio of E2 (inc) to P4 (dec)

This change stimulates Prostaglandin release

Question 6

What hormones is parturition driven by? (maternal)

Answer 6

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

Question 7

What is the Ferguson Reflex?

Answer 7

Fetus contacts cervix –> stimulates oxytocin release from post pit

Question 8

What can induce premature labor?

Answer 8

ACTH or cortisol, or corticosteroids

*Caution when rx’ing for pregnant animals

Question 9

When does labor typically happen?

Answer 9

At night –> quiet, less stressful for mom

*mom doesn’t have much control over labor timing, but stress can delay a bit

Question 10

Parturition in CL dependent spp

Answer 10

Fetal cortisol initiates parturition –> placental E2 inc –> PGF release causes regression of maternal CL (luteolysis) –> labor begins as maternal P4 conc. decline

Question 11

Parturition in litter bearing spp

Answer 11

Parturition is initiated by signals from entire litter –> one early maturing fetus cannot trigger labor alone

rapidly maturing fetuses may be favored

Question 12

How many stages of labor are there?

Answer 12

3

Question 13

Stage 1 - Initial contractions

onset, end, CS

Answer 13

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

Question 14

Stage 1 - Duration

bitch, cow, mare

Answer 14

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)

Question 15

Stage 1 - fetal movements

Answer 15

Head and forelimbs extend

Body rotates into dorsal position

Question 16

Stage 2 - Delivery of fetus

onset, end, CS

Answer 16

Onset: rupture of chorioallantois (water breaks)

End: delivery of fetus

CS: active straining, appearance of translucent membrane (amnion at vulva), birth of fetus

Question 17

Stage 2 - Duration

cow, mare, bitch

Answer 17

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

Question 18

Stage 2 - single vs multiple fetuses

Answer 18

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

Question 19

Stage 3 - passage of fetal membranes (Placental)

Onset, end

Answer 19

Onset: delivery of fetus

End: passage of membranes

Question 20

Stage 3 - duration

mare, cow, bitch

Answer 20

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

Question 21

How can we induce labor?

1. ruminants
2. CL dep spp
3. horses

Answer 21

1. corticosteroids
2. prostaglandins
3. oxytocin