Normal Parturition - Anatomy & Physiology
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BACK TO REPRODUCTIVE SYSTEM
BACK TO PARTURITION
BACK TO REPRODUCTIVE SYSTEM
BACK TO PARTURITION
Species | Mare | Cow | Ewe | Sow | Bitch |
---|---|---|---|---|---|
Stage 1: Contractions and Cervical Dilation | 1-4 hours | 2-6 hours | 2-6 hours | 2-12 hours | 6-12 hours |
Stage 2: Foetal Expulsion | 12-30 minutes | 30-60 minutes | 30-120 minutes | 150-180 minutes | 6 hours (up to 24 hours with large litters) |
Stage 3: Placental Expulsion | 1 hour | 6-12 hours | 5-8 hours | 1-4 hours | Placenta Exits with Foetus |
Parturition is the Process by which the conceptus (foetus, placenta and placental membranes) are expelled from the Uterus requires:
- Cervical Softening
- Coordinated Myometrial Contraction
- Voluntary contraction of abdominal muscles
Stage 3: Placental Expulsion
In most species, expulsion of foetal membranes quickly follows expulsion of the foetus.
- After the birth of the young, regular abdominal contractions largely cease.
- Myometrial contractions persist.
- Decreased amplitude, but become more frequent and less regular.
- Important for dehiscence and expulsion of foetal membranes.
- Waves of contractions from uterus to the cervix persist.
- Act in a peristaltic fashion in the cow and sow in the reverse direction.
Placental Changes
During the last 5 days of gestation, there are changes in the placenta.
- Collaginisation of the placentome.
- Flattening of maternal crypt epithelium.
- Leucocyte migration and increased activity.
- Reduction of binucleate cells in the trophectoderm.
- Weakening of the acellular protein layer between cotyledonary and caruncular epithelium.
Contractions
- Open endometrial crypts
- Foetal villi have shrunk due to the escape of blood from the foetal side of the placenta when the umbillical cord ruptures.
- Myometrial contractions aid exsanguination of the placenta.
- Separation of foetal membranes.
- Apex of the allantochorionic sac becomes inverted.
- As the sac is 'rolled' down the uterine horns, foetal villi are drawn out of the crypts.
- When a large portion becomes detached and inverted, it forms a mass in the maternal pelvis.
- Stimulates reflex contractions of abdominal muscles.
- Completes expulsion of the allantochorionic sac.
- In polytocious species, dehisence and expulsion of foetal membranes are interspersed with births of the young.
- Only expulsion of the last afterbirth stimulates abdominal contractions.
- The final stage of allantochorionic expulsion lasts 1 hour (mare) - 6 hours (cow).
- Domestic animals normally eat the afterbirth.
- Not the mare or camelids.
Parturition Behaviour
Mare
Stage 1
- Mammary hypertrophy, waxing of the teats and possible escape of milk from the glands.
- Patchy sweating behind the elbows and around the flanks.
- Commences ~4 hours before the birth of the foal and increases as the stage progresses.
- Yawns
- No indication of pain.
- Food is taken readily
- Respirations are normal
- Pulse is ~60
- Body temperature may become slightly subnormal (36.5-37◦C).
- Restlessness, wanders aimlessly.
- Tail is frequently raised or held to one side.
- May swish the tail or slap it against the anus.
- Kicking of the abdomen
- Towards the end of this stage:
- Crouching
- Straddling of hindlimbs
- Going down on knees or sternum and rising again
- Glancing at flank
- This stage terminates with the rupture of the allantochorionic membrane and the escape of allantoic fluid from the vulva.
- No visible straining during this period.
Stage 2
- Abrupt onset, lasts~17 minutes
- Appearance of the amnion or commencement of forceful straining
- Not much delay between them, often coincide.
- Soon after straining begins, the mare goes down.
- Lies on her side with the limbs extended
- Generally remains in this position until the foal is born.
- Transperent blue/white 'water bag' (amnion) visible at the vulva
- Quickly followed by the appearance in it of a digit.
- Straining at regular intervals.
- Each comprises 3/4 powerful expulsive efforts followed by a period of rest.
- Generally 3 minutes long
- One forelimb procedes the other by 7-8cm
- One elbow passes through the pelvic inlet before the other preventing minimal obstruction.
- Head is usually in the oblique position, but may be transverse with the cheek lying on the limbs.
- Greates and longest effort is with birth of the head.
- After expulsion of the foal, the mare may remain on her side exhausted for up to 30 minutes.
- Umbillical cord is intact when the foal is born.
- Subsequently ruptures 5-8cm below the belly due to movement of the mare or foal.
- Foal is usually born within the amnion, which is ruptured by movements of the forelegs.
- Lower portions of the hindlimbs often remain within the vagina for minutes after the rest of the foal is born.
Stage 3
- Membranes expelled quickly after the birth of the foal.
- Usually within 3 hours.
- Duration of stage 3 is ~30 minutes.
- Afterbirth is expelled by myometrial contractions with no straining.
Cow
Stage 1
- Lasts ~6 hours
- Relaxing of pelvic ligaments.
- Mammary secretions change from transparent,honey-like to opaque, cellular colostrum.
- Body temperature subnormal by ~0.6◦C.
- Parturition will begin 12 hours after complete relaxation of the posterior borders of the sacrosciatic ligaments.
- Heifers may show signs of abdominal pain for up to 24 hours before the cervix is fully dilated.
- Occasional straining may occur.
- Picks at feed, irregular rumination
- 'Lowing'
- Kicking of the abdomen
- Restless, may stand with her back arched and tail raised.
- May go down and rise again frequently
- Pulse rate often increased to 80-90.
Stage 2
- Lasts 30 minutes - 4 hours
- Longer in heifers than in cows
- Male calves take longer to be born
- Onset marked by the appearance of the amnoin ('water bag') at the vulva.
- Less frequent straining
- Remains standing at first
- During passage of the head through the vulva, the cow normally goes down and remains recumbent until the calf is born.
- May lie on her side or in sternal recumbency.
- Placental separation occurs more slowly than in the mare.
- Umbillical cord of the calf is shorter than in the foal and generally ruptures as the calf falls from the vulva.
Stage 3
- Expulsion of the foetal membranes usually occurs ~6 hours after the birth of the calf.
- After 24 hours consider a pathological cause for retained placenta.
- Cow will eat the foetal membranes.
Ewe
Similar to the cow, except incidence of twinning and triplets is high.
Stage 2
- Completed within 1 hour usually.
- Lambs nrmally in enterior presentation.
- In twin births where one foetus occupies each horn, one horn develops contractions before the other.
- Hence distocia due to simultaneous presentation is more common when both foetuses occupy the same horn.
Stage 3
- Placenta usually expelled within 2-3 hours after birth of the lamb.
Sow
Stage 1
Stage 2
Stage 3
Bitch
Stage 1
- Lasts ~ 12 hours
- Prepares the bed
- If carrying one pup, the onset of lactation coincides with parturition.
- If carrying multiple pups, milk may be expressed from the teats several days prior to the onset of parturition.
- Body temperature subnormal by at least 1.2◦C within 24 hours before the onset of labour.
- Restless
- Indifferent to food
- Panting
Stage 2
- Depends upon the number of foetuses, but usually lasts ~6 hours.
- Straining indicates the onset of the second stage.
- Bitch remains in her bed in sternal recumbency
- 'Water bag' of the first foetus appears at the vulva, and attains the size of a golf ball.
- Bitch licks the vulva vigorously and usually ruptures the 'water bag'.
- Delivery of the head requires the greates effort, once this is bord the rest of the foetus follows easily.
- Expulsion of the first foetus may take up to 1 hour.
- Umbillical cord is intact at birth, the mother will soon bite it away.
- Bitch rests for a time after the birth of the first puppy.
- Lies licking the puppy, which soon begins to suckle.
- Pays frequent attention to the vulva and licks any discharge.
- Foetal membranes generally voided in 10-15 minutes and eaten by the bitch.
- Straining recommences after a delay of 30 minutes - 2 hours.
- Effort and time required for subsequent deliveries is usually less than the first.
- May rest in between subsequent deliveries, but may not. The period of rest is also very variable.
- Puppies tend to be expelled from alternate horns (unlike the sow).
- Expulsion of foetal membranes is also irregular, they may come out individually, or the next puppy may be born with the membranes of its predeccessor around its neck.
Stage 3
- Membranes of the last foetus are expelled with it or shortly afterwards.
- Discharge is dark green in colour.
- Due to breakdown of the marginal haematoma, blood pigment biliverdin escapes.
Cat
During the last week of pregnancy, the queen seeks a nesting area. This is usually a quiet, undisturbed spot but some house cats will demand more human contact.Mammary development becomes noticable in the last week of pregnancy, especially in maiden cats. Rectal temperature may fall a few days before parturition, but this is not a reliable indicator.
Stage 1
- Restless
- Frequently visits the site for kittening
- Occasionally lies down and will strain unproductively.
Stage 2
- Straining in lateral recumbency.
- Rapid expulsion of kittens with a short interval between each birth.
- Parturition usually complete within a few hours.
- If the queen is alarmed, this may disrupt the pattern and she may move the kittens to a new area before parturition resumes.
- Soon after birth the kittens begin to suckle.
Stage 3
- Placentae usually expelled still attached to the foetus or shortly afterwards.
- Consumed by the queen.
- Breakdown of marginal haematoma releases biliverdin, giving the discharge a brownish colour.