Wk. 10Parturition Flashcards
Hormones involved in gestation
Placental +/- CL progesterone is high throughout pregnancy (the pregnancy block):
- Creates -ve feedback on HPG axis (stops cycling)
- Keeps levels of E2 low (this is necessary for parturition though)
- Limits myometrial contraction (don’t want this until parturition)
Hormonal changes in lead up to parturition: what do we see?
Late in gestation, E2 begins to rise – why?
- Uterine crowding (limited space) triggers fetal ACTH secretion
- ACTH prompts fetal cortisol secretion
- Fetal cortisol triggers conversion of P4 to E2
Fetal cortisol causes causes placenta to secrete PGF2a, leading to luteolysis (CL of pregnancy)
P4 is dropping due to both:
- Conversion to E2
- Luteolysis
Fetal + placental hormones are key regulators of parturition
Parturition = incr. fetal cortisol + incr. E2 + decr. P4
What does conversion of P4 to E2 allow for before parturition?
Elevated E2 and PGF2a:
- Increased myometrial contractions
- Increased uterine pressure
- Increased stimulation of cervix
- Increased secretion (cervix, vagina) Also leads to secretion of two
Parturition – the 3 stages
Stage 1 (initiation of contractions)
stage 2 (delivery of foetus)
stage 3 (delivery of palcenta)
Stage 1 – initiation
- Initiation of myometrial contractions & cervixal dilation
- Tail elevation & twitching, mucus discharge, restlessness/anxiety, nesting behaviour
Stage 2 – Delivery of fetus (active labour)
- Strong uterine/abdominal contractions, relaxation of pelvic ligaments, mucus production, movement of fetus from uterus through cervix + vagina
- Straining during contractions, appearance of membranes and/or fetus at vulva, resting between offspring in polytocous sp.
Potential problem - DYSTOCIA
Potential problem - DYSTOCIA
Stage 3 – Delivery of placenta
- Weaker uterine contractions, vasoconstriction at point of placenta attachment (stops outflow of blood), movement of remaining placenta from uterus through cervix + vagina
- Appearance of membranes at vulva Potential problem – retained membranes
3 stages across species - timing of contractions, delivery of foetus, delivery of placenta
Average length of gestation is known for all domestic species, but how might we predict impending parturition more accurately for a given dam?
- Look for stage 1 behaviours (e.g. nesting, increased movement, discharge)
- Testing hormones in blood
- Udder filling with milk
- Follow fetus growth (e.g. have they reached biggest size, are they filling out uterus)
Calving signs - cattle (cow)
- Normal clinical signs
Timing* - when do we need to intervene if no progression time wise/time that placenta has not passed
Normal clinical signs
- sternal recumbency
- straining with contractions (stage 2)
- standing and licking calf once born
- Placentophagy
Timing** - when do we need to intervene
- if no progression >2 hours of active labour something is wrong
- placenta not passed >12 hours after calf - retained placenta
Lambing – sheep
- Predicting parturition date - common signs
- Normal clinical signs
Timing* when do you need to intervene
- Predicting parturition:
- Loose vulva, udder development and firm teats, isolation from flock
- Normal clinical signs
- Sternal recumbency or standing
- Straining with contraction (Stage 2), vocalisation
- Standing and licking lamb once born
- Placentophagy sometimes
- Timing - when to intervene
- If no progression >1 hour of active labour
Placenta not passed >12 hours after lamb
- If no progression >1 hour of active labour
Foaling - horse (mare)
- predicting parturition date
- normal clinical signs
- timing - when do you need to intervene
- Predicting date of parturition:
- Udder development
- Perineal relaxation
- Waxing of teats (48-24 hours before)
- Relaxed/swollen vulva
- Increasing Ca2+ concentration in milk
- Normal clinical signs
- Lateral recumbency or standing
- Straining with contractions (S2)
- May stand between contraction, standing and licking foal)
- Timing - when to intervene
- If no progression >20mins of active labour
Placenta not passed >6 hours after foal
- If no progression >20mins of active labour
Farrowing - pig (sow)
- Predicting date of parturition
- Normal clinical signs
Timing - when to intervene
Predicting date of parturition
Normal clinical signs
- Lateral recumbency
- Mild straining with contractions (s2) Timing – when do you need to intervene
- If >30 mins of active labour between piglets
- If # placentas delivered = (not equal) # piglets
- Predicting date of parturition
- Normal clinical signs
Timing - when do you need to intervene
- Normal clinical signs
Predicting date of parturition
Normal clinical signs
- Lateral recumbency
- Straining with contractions (s2)
- Panting & vocalisation
- Licking puppies once born
Timing – when do you need to intervene
- If >2 hours of active labour between puppies
- If # placentas delivered = (not equal) # puppies
Queening - cat (queen)
- Predicting date of parturition
- Normal clinical signs
Timing - when do you need to intervene
Predicting date of parturition
Normal clinical signs
- Lateral recumbency or standing
- Straining with contractions (s2)
- Licking kittens once born
Timing – when do you need to intervene
- If >1 hour of active labour between kittens
- If # placentas delivered = (not equal) # kittens
A bitch has just finished stage 1 of parturition. What has not occurred yet out of the following?
- Conversion of P4 to E2
- Strong coordinated myometrial contractions
- Peak of foetal cortisol
- Cervical dilation
- Production of colostrum
- Strong coordinated myometrial contractions
- This occurs in stage 2
Why?
- Conversion of P4 to E2 has already occurred
- Peak of foetal cortisol has already occurred too
- Cervical dilation occurs during stage 1
Production of colostrum also already occurred
Role of oxytocin and relaxin during parturition
Oxytocin is produced by hypothalamus
(paraventricular nucleus) in response to physical pressure on cervix – drives uterine contractions, creating a positive feedback loop (Ferguson reflex)
Relaxin (secreted by CL or placenta) softens cervix and relaxes pelvic ligaments
Describe normal events of stages 2 and 3 of parturition and their expected timeframes. Placenta is hanging out at 12hours (stage 3)- would you be concerned with how Juno is progressing?
- Stage 1 = initiation of contractions
- Stage 2 = delivery of foetus –> 0.5-1 hour –> intervene after this
i. Stage 2 we have increased and strong myometrial contractions, relaxin and oxytocin to promote this (relax pelvic ligaments + mucous production). Movement of foetus from uterus and vagina
ii. Clinical signs (Csx) = straining during contractions appearance of membrane or foetus, resting between offspring,- Stage 3 = delivery of placenta --> 6-12 hours --> intervene after this i. Weaker uterine contractions ii. Vasoconstriction occurs at the point of placenta attachment iii. Movement of placenta from uterus --> cervix --> vagina iv. Signs: appearance of placenta/membranes at the vulva
As the timeframe is 6-12 hours, and it has been 12 hours and we can see the placenta hanging out, wouldn’t be too concerned. Cows don’t require much intervention, although would probably intervene with pulling placenta out if it does not expell soon.
Compare duration of stage 3 parturition in mare and cow (hours) - how might placenta antomy influence these differences:
- Cow: stage 3 = 6-12hours for placenta delivery
i. Cows have a multicotylendonary epitheliochorial placenta. Have placentomes (caruncle + cotylendon)
ii. Cows commonly retain placenta, especially if twinning. - Mare: stage 3 = 1hour for placenta delivery
i. Mare is much shorter time frame for placenta delivery
ii. In horses, everything happens a lot quicker
iii. Horses have diffuse, epitheliochorial placenta, endometrial cups, cervical star
In mares = >6hrs should intervene. Prolonged retention could = secondary problems such as colic.
Why does E2 rise in late gestation?
- Uterine crowding - triggers foetal release of ACTH secretion
- ACTH prompts foetal cortisol secretion
Foetal cortisol triggers conversion of P4 to E2
What does foetal cortisol cause placenta to secrete
- PGF2a - leading to luteolysis (CL of pregnancy)
What foetal and placental hormones regulate parturition:
- Increased foetal cortisol
- Increased E2
Decreased P4
List sequence of events caused by elevated E2 and PGF2a during parturition (labour)
- Increased myometrial contractions (uterine)
- Increased uterine pressure
- This pressure stimulates the cervix (drives foetus down to the placenta)
- Increased secretion of fluids (cervix and vagina)
- Also leads to secretion of other hormones
- Oxytocin - by increased pressure
Relaxin - PGF2a
- Oxytocin - by increased pressure
timing for initiation, delivery of foetus, placental delivery in cow:
- initiation: 2-6hrs
- delivery: 0.5-1hr
- placenta: 6-12hr
initiation, delivery and placental delivery for mare:
- intitiation:1-4hr
- delivery:15-30mins
- placenta: 1hr
initiation, delivery of foetus, placental delivery timing for bitch
initiation: 6-12hr
delivery: 6-24hr
timing between offspring 30min-2hr
placental: 15min
initiation, delivery of foetus and placental delivery timing in sow:
initiation: 2-12hr
delivery: 2.5-3hr
timing between offspring: 10-20min
placental: 1-4hr
