Parturition Flashcards
Hormones in gestation, the 3 things that this hormone does
Placental +/- CL progesterone is high throughout pregnancy (the pregnancy block):
- Creates -ve feedback on HPG axis (stops cycling)
- Keeps levels of E2 low
- Limits myometrial contraction
Hormonal changes in lead up to parturition 7 steps
- Uterine crowding = ACTH secretion from foetus
- ACTH = cortisol secretion
- Foetal cortisol triggers P4 to convert to E2
- Foetal cortisol makes the placenta start to secrete PGF2alpha
- PGF2alpha causes luteolysis (Corpus Leutum)
- Progesterone levels drop because of conversion and breakdown of CL
- On the road to parturition
Hormonal changes during parturition, what starts it, what are the feedback cycles and what drops and why?
Consequences of elevated E2 and PGF2a:
- Increased myometrial contractions
- Increased uterine pressure
- Increased stimulation of cervix
- Increased secretion (cervix, vagina) Also leads to secretion of two other important hormones – oxytoxin and relaxin
Hormonal changes drive cascade of physiological responses
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
Parturition – 3 stages
Stage 1 (initiation)àstage 2 (fetus)àstage 3 (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
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 - cattle
Predicting date of parturition
Normal clinical signs
- Sternal recumbency
- Straining with
contractions (s2)
- Standing an licking calf
once born
- Placentophagy (not always)
Timing – when do you need to intervene
- If no progression >2 hours of active labour
- Placenta not passed >12 hours after calf
Lambing – sheep
Predicting date of parturition
Normal clinical signs
- Sternal recumbency or standing
- Straining with contractions (s2),
vocalisation
- Standing and licking lamb once born
- Placentophagy (maybe?)
Timing – when do you need to intervene
- If no progression >1 hour of active labour
- Placenta not passed >12 hours after lambs
Foaling - horse
Predicting date of parturition
Normal clinical signs
- Lateral recumbency or standing
- Straining with contractions (s2)
- May stand between contractions (2-3min)
- Standing and licking foal once born Timing – when do you need to intervene
- If no progression >20 min of active labour
- Placenta not passed >6 hours after foal
Farrowing - pig
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
Whelping - dog
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
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 yet occurred?
Answer B.
Cervical dilation happens during s1. All others happen before s1
