Parturition: Physiology and Process

• Parturition refers to the physiological process where the pregnant uterus delivers the fetus and placenta.
• The term originates from the Latin word "parturire", meaning "to be ready to bear a young one."

Pathways of Parturition

• Fetal stress, due to the uterus being too small or insufficient oxygen, triggers the release of fetal cortisol.
• Cortisol converts progesterone to estrogen, leading to lubrication of the birth canal and myometrial contractions.
• Increased cervical stimulation leads to the production of oxytocin, which further stimulates uterine contractions.
• Cortisol also stimulates the release of prostaglandin F2a (PGF2a), which restricts blood supply to the ovary, causing lysis of the corpus luteum (CL) and decreased progesterone production.
• PGF2a also leads to the production of relaxin, relaxing pelvic ligaments and expanding the pelvic cavity.

Symptoms of Approaching Parturition for Cows

• Udder enlargement occurs up to 4 months before parturition in heifers and 1 week in cows.
• Vaginal discharge is observed around 7 months.
• Two months prior to parturition, assessment can be made to guide bringing the cow to the calving pen.
• Relaxed pelvic ligaments and a raised tail head are observed 24-48 hours prior, indicating the cow should be in the calving pen.
• Sinking of the pelvis is also noticeable.
• Anorexia may be observed for 1-2 days.

Symptoms of Approaching Parturition for Mares

• Udder development begins 2-6 weeks before foaling.
• Waxing of teats, with solidifying colostrum, occurs 1-4 days before foaling.
• Relaxation in the pelvic region occurs gradually during the last 7-14 days of gestation.

Symptoms of Approaching Parturition for Sows

• Reduced appetite and restlessness.
• Chewing and moving bedding.

Symptoms of Approaching Parturition for Ewes

• Vulva stretches out, becomes red and swollen.
• Ewe may miss a feeding and separate from the flock shortly before labor.

Symptoms of Approaching Parturition for Does

• Udder enlargement starts 1-6 weeks before kidding.
• Hollowness is noticeable on either side of the doe's tail.
• Isolation from the rest of the herd.
• Enlarged udder and teats begin to fill with milk.

Symptoms of Approaching Parturition for Bitches

• Temperature decreases by around 1°C 1-2 days prior to whelping due to low progesterone levels, warranting twice-daily temperature monitoring.
• Restlessness and decreased appetite.
• Mild clear vaginal discharge 2-3 days before whelping is apparent, accompanied by mild vomiting and diarrhea.

Symptoms of Approaching Parturition for Queens

• Nervousness, overgrooming, and panting.
• Stops eating on the final day of pregnancy.
• Drop in rectal temperature to less than 37.5°C in the last 24 hours signals impending labor.
• Milk may appear in the mammary glands 24-48 hours before.
• Preference for seclusion during birthing.

Further signs for Mares

• Udder enlargement and changes in mammary secretions in the last 2 weeks.
• Engorgement of the udder occurs within the last few days before foaling.
• Accumulation of waxy secretion on teat ends 1-4 days before foaling.

Fetal Disposition

• The fetus becomes more active and progressively rotates from a ventral to dorsal position.
• Forelimbs, head, and neck extend in foals and puppies, while only the head and neck extend in calves and lambs.
• Flexed knees of the calf first occupy the dilating cervix, with digits entering the cervix after 30 minutes.
• Normally, the back of the fetus is against the pelvis (dorsosacrum, dorsopubis, dorsolateral).
• Abnormal limb positions include carpalflexion, shoulderflexion, and elbowflexion.

First Stage of Labor

• Involves dilation of the cervix.
• Consists of preparation of the birth canal and fetus for expulsion.
• Changes are not visible externally.
• Signs of discomfort, mild colic, and restlessness are seen, along with elevated pulse and respiratory rate and a drop in body temperature.
• Structure of the cervix changes.
• Myometrial contractions begin.
• Fetus assumes proper disposition for expulsion.

Cervical Changes During First Stage

• Ground substance loosing due to changes in collagen components.
• The cervix dilates, starting with the external os then the is.
• Water incorporation permits collagen fibers separation with tension.
• Shortening of the cervix and dilation of the internal os occurs simultaneously.
• The vagina and uterus become one continuous canal, tightly engaged by the distended allantochorion.

Onset of Myometrial Contractions

• Presence of cervicotubular and tubular-cervical contractions.
• Cervicotubular contractions prevent premature displacement of the fetus/es for orderly expulsion from the horns in pigs, dogs, cats.
• Uncoordinated waves changing to regular, coordinated peristaltic type.
• Frequency increases from 12-24 per hour in the last 2 hours to 48 per hour just before expulsion (30 per hour in ewes).

Duration of First Stage of Labor by Species

• Cow: 4-24 hours.
• Buffalo: 1-12 hours.
• Mare: 1-12 hours.
• Ewe: 6-12 hours.
• Sow: 12-24 hours.
• Bitch: 4-24 hours.
• Cat: 2-12 hours.

Second Stage of Labor

• Characterized by the expulsion of the fetus.
• In polytocous species (dog, cat, sow), the 2nd and 3rd stages cannot be separated.
• A sign is the appearance of abdominal contractions superimposed upon each set of myometrial contractions.
• Ferguson's reflex triggers a self-sustaining cycle of uterine contractions and oxytocin release.
• The allantochorionic sac ruptures.
• The "water bag" (amnion) appears at the vulva.
• Fetal head appears at the vulva with maximal uterine and abdominal muscle contractions.
• The fetal thorax passes through the vulva, followed by expulsion of hips and hindlimbs.
• The amnion ruptures, allowing the fetus to respire.
• Presentation: anterior, dorsal, extended
• Position: dorsal
• Posture: extended
• In polytocous species (bitch, sow, queen), 40-45% of fetuses normally delivered in posterior presentation.

Duration of Second Stage of Labor by Species

• Cow/Buffalo: 30 minutes - 3 hours.
• Buffalo: 45-90 minutes.
• Mare: 30 minutes.
• Ewe/Doe: 30 minutes - 1 hour.
• Sow: 30 minutes - 4 hours.
• Bitch: 1st puppy within 2 hours; 5-60 minutes between puppies; total time up to 24 hours.
• Cat: 1st kitten within 5-60 minutes; 5-60 minutes between kittens.

Third Stage of Labor

• Characterized by the Expulsion of the placenta
• Cessation of regular abdominal contractions is seen.
• Decreased amplitude of myometrial contractions occurs for dehiscence and expulsion of fetal membranes.
• Waves of contractions occur from the uterine tube to cervix, reversing in the cow and sow.
• Weakening of the acellular layer of adhesive protein.
• Collagenization of placentome and flattening of maternal crypt epithelium in cow, starting 5 days before.
• Shrinking of fetal villi due to loss of fetal turgidity from escape of blood from fetal side of placenta with rupture of umbilicus.
• Separation of fetal membranes due to early degenerative maturational changes in ewe and cow.
• Apex of allantochorionic sac is inverted and sac is 'rolled down' the cornua, drawing out fetal villi from crypts.
• Mass forms in maternal pelvis stimulating abdominal contractions
• Domestic animals eat placenta except for the mare.
• In polytocous species, dehiscence and expulsion of fetal membranes are interspersed with fetal births.
• Sucking reflex in mares triggers the release of oxytocin, promoting milk letdown and augmenting myometrial contraction.
• Sucking results in greater synchrony of contractions and increase in number of tubocervical contractions.

Duration of Third Stage of Labor by Species

• Cow: 12-16 hours.
• Buffalo: 7-12 hours.
• Mare: 30 minutes - 3 hours.
• Ewe 3-6 hours.
• Sow: After 2-3 piglets or 4 hours post-farrowing.
• Bitch/Queen: Along with puppy; or within 2 hours of last puppy/kitten.

Dystocia

• Dystocia refers to difficult or abnormal labor.

Predisposing Factors of Dystocia: Heredity

• Specific breeds are more prone to dystocia.
• Certain defects like hydrocephalus and achondroplasia are more common.

Predisposing Factors of Dystocia: Nutrition and Management

• Over or under nutrition can lead to small dam size
• Inadequate mating
• Poor feed management

Predisposing Factors of Dystocia: Traumatic

• Ventral hernia; rupture of the prepubic tendon.

Predisposing Factors of Dystocia: Miscellaneous

• Calcium deficiency.

Maternal Expulsive Forces: Uterine

• Uterine inertia.

Maternal Issues: Primary Uterine Inertia

• Myometrial defect: over stretching, degeneration, uterine infection, small litter size or heredity.
• Biochemical deficiencies: estrogen, oxytocin, PGF-2a, relaxin, calcium, glucose.
• Environmental disturbances.
• Nervousness.
• Oligomanios: low amniotic fluid volume) - seen in premature birth.
• Lack of exercise.

Maternal Issues: Secondary Uterine Inertia

• Exhaustion.

Treatment for Uterine Inertia

• Calcium borogluconate with or without forced extraction.

Uterine Rupture

• Can occur spontaneously due to a weak spot.
• rolling during treatment or uterine torsion.
• Large ruptures leads to sudden death.
• Small ruptures cause transient colic without fetal delivery, with intestines protruding from the vulva.
• Treatment involves laparotomy and repair.

Uterine Torsion

• Palpates the relative positions of the broad ligaments to diagnose.
• It's considered a 180 clockwise and 180 counterclockwise uterine torsion.
• Schaffer method ("plank in a flank" method) involves rolling cow around fetus while keeping the uterus in place manually.

Maternal Expulsive Forces: Abdominal

• Inability to strain due to issues.
• Diaphragmatic or abdominal hernia or debility.
• Forced extraction

Maternal Issues: Insufficient Dilation of Birth Canal

• Inadequate pelvis due to fracture, exostoses, immaturity, breed, and neoplasia which Require C-section
• Dilation failure, congenital defects, fibrosis in the uterus, cervix, and vagina.
• Insufficient cervical or vaginal dilation.

Failure of Cervical Dilation

• Less common in buffalo compared to cattle due to more capacious pelvis, large area of ileum and free and easily separable 5th sacral vertebra.
• Common in sheep and goats, known as ring womb.
• Vaginal examination reveals only 1 or 2 fingers able to pass.
• Uterine torsion is ruled out.

Treatment of Failure of Cervical Dilation

• B-2 adrenergics such as salbutamol, terbutaline, isoxsuprine HCI (50-100 mg IM or IV for cows, 100-150 mg for mares and 10-40 mg for sheep and goats) with manual manipulation, though results are inconsistent.
• Clenbuterol 0.3 mg IV or IM.
• Misoprostol (local application) for mares but not in cattle.
• Partial cervicotomy is performed if fetus already emphysematous.
• Cesarean section is performed if drug therapy fails.

Failure of Vaginal Dilation

• Abscesses: identify and drain pre-partum.
• Large tumors: surgical excision (debulking) pre-partum.
• Large vaginal hematoma: C section.
• Vaginal cystocoele : push back legs of fetus and replace bladder 1st.
• Vulvar stenosis: forced extraction with or without episiotomy.

Fetal Death

• Stage 1 labor may not be initiated.
• Fetal movements lacking (LA); Xray (SA).
• Tx. forced extraction, fetotomy, or C-section

Fetal Defects

• Ascites, hydrocephalus, anasarca (hydrops foetalis).
• Hydrocephalus can be treated with mannitol, vitamin A, and antibiotics with success.
• Anasarca results from a recessive gene mutation.
• Treatment involves forced extraction, fetotomy, C section.

Fetal Oversize

• Fetal monsters; disproportionate mating.
• Fetus with relation to the pelvis (feto-maternal/feto-pelvic disproportion). Common in heifers that calve at <2 years of age.

Treatment for Fetal Oversize

• Forced extraction or C-section if alive.

Fetal Maldisposition

• Malpresentation (Transverse, lateral, vertical)
• Malposition (Dorsopubic, dorso-ilial, oblique)
• Malposture

Abnormal Presentations

• Transverse presentation

Rotation or Retropulsion Obstetric Manuever

• Pushing fetus forward in uterus to obtain adequate space for correction of fetal part in an abnormal presentation, position and posture.

Rotation Obsteric Maneuver in Mares

• Turn the fetus on its long axis to correct it with hands.

Version

• Effecting change in fetal presentation to 90° .
• Transverse presentation modify to longitudinal presentation

Mutation/Correction Obsteric Manuevers

• Change of the presentation. position or posture to normal
• Includes repulsion, rotation, version

Obsteric Manuever Requirements

• Full cercical dilation with lubrication and caudal spinal

Forced Extraction

• Pull out the fetus from birth canals using force.
• Anesthesia with adequate lubrication needs in a downard arc

Fetotomy

• Reducing the volume of dead or the fetus which sacrified.
• Done due due to can't delivery

Fetotomy Advantages

• Rapid reduces in size for easier vaginal operation without sergery.
• Less care and short recovery

Fetotomy Diadvantages

• Take long time with injuries
• Indicated deformities of the cervix, irreducible dislocation of the fetus, muscle contraction etc

Damage to the Lumbosacral Plexus

• Due to extra force extract for oversized fetus in "hip lock",
• Type includes paralysis, gluteal paralysis with sign weakness and difficulty in rising

Uterine Prolapse

• Uncommon for mares associated wit gestation with poor proclivity with strain in stage 3. Can cuase flaccidity

Post partum haemorrage

• May be normal in carnivores with excessive force used

Hematoma to Vulva

• Usually of extracts force in one vulva with prolaspe as with prolaps,or cyst with spontaneious. May takes days.

Perianal lancerate

• 1/3 degree of infection inrectocagal , muscular is in floor

Perineal Lacerations

• usually hoof in vaginalis with early position and repair