Initiation of Parturition

Question 1

What are the signs of impending parturition?

Answer 1

• expectancy dates
• mammary enlargement and colostrum production
• enlargement and laxity of the vulva (elongation)
• pelvic (sacrosciatic) ligament relaxation and softening of the perineum area
• isolation and decrease in appetite

Question 2

A longer gestation has a longer/shorter deviation?

Answer 2

longer (days vs. weeks)

Question 3

What changes in animal behavior can be noted in stage one of Parturition?

Answer 3

• they separate themselves
• may note signs of colic (treading, looking at flank, restless, pawing at ground)
• may become anorexic
• tail may be raised
• possible vaginal discharge (serosanguinous vs. clear mucoid)
• may drip colostrum/milk

Question 4

What triggers the onset of parturition?

Answer 4

the fetus

Question 5

the ________ is necessary for the trigger of parturition

Answer 5

the fetal hypothalamo-pituitary-adrenal axis

Question 6

Near the end of gestation, ________ appears to be the stimulus for _____ secretion by the fetal pituitary

Answer 6

space limitation

ACTH

Question 7

the fetal pituitary stimulates secretion of ______

Answer 7

adrenal corticoids (cortisol)

Question 8

what does the elevation of adrenal corticoids initiate?

Answer 8

a cascade of events that lead to dramatic changes in the endocrinology of the dam

Question 9

what drastic changes in the dam’s endocrinology does the fetal elevation of adrenal corticoids lead to?

Answer 9

• removal of the myometrial “progresterone block”

- increased repro. tract secretions (cervix)

Question 10

The corticoids from the fetus activate enzymes that cause what to happen to progesterone?

Answer 10

convert it to estradiol

Question 11

results of hormonal changes in fetus and dam

Answer 11

• final maturation of the fetus (cortisol enhances surfactant production)
• expansion of the birth canal
• maternal behavior
• synthesis and ejection of milk
• initiation of uterine contractions
• termination of pregnancy

Question 12

what are the initial hormone changes seen?

Answer 12

• decreased progesterone

- increased estrogen

Question 13

what does the initial decrease in progesterone do during initiation of parturition?

Answer 13

removes the block on uterine contractions

Question 14

what does the initial increase in estrogen do during initiation of parturition?

Answer 14

• uterus responsive to induction of contractions
• induction of oxytocin receptors
• pelvic ligaments soften (tail head sinks; sacrosciatic ligaments)
• cervix softens
• swelling of vulva - collagenase breaks down collagen

Question 15

when are expectancy dates more precise when predicting parturition?

Answer 15

if assistance was provided during the breeding (eg., progesterone timing in the bitch, timed AI events, etc.)

Question 16

what “tests” can be performed to note initiation of parturition?

Answer 16

• daily rectal temps in dogs to see transient drop (<99F)
• P4 levels (generally not practical)
• Milk calcium test in mares (if >200, foaling in 24-72 hr)

Question 17

Stage I of parturition involves what?

Answer 17

dilation of the cervix

Question 18

what hormones induce uterine contractions?

Answer 18

estrogen and PGF2a

Question 19

When the fetus pushes against the cervix, what can occur?

Answer 19

• amnion dilates the cervix
• chorioallantoic membrane may break (1st water bag)
• pressure of the fetus on the cervix may stim. oxytocin release and reflex contractions of abdominal muscles

Question 20

impediments to initiation of parturition

Answer 20

• hypocalcemia (milk fever)
• uterine torsion
• fetal death