Initiation of Parturition Flashcards
What triggers the onset of parturition?
Fetal stress
How does fetal stress initiate parturition?
Maturation of the fetal HPA axis
Small space leads to fetal stress, increasing cortisol levels, leading to a chain of events
How do progesterone levels affect the onset of parturition?
Decreased progesterone removed the “block” on uterine contractions
How do estrogen levels affect the onset of parturition?
Increased estrogen causes induction of oxytocin receptors, pelvic ligament relaxation, vulvar swelling, and uterus becomes responsive to induction of contractions
Which hormones cause the pelvic ligaments to relax & what other clinical signs would be noticeable?
Relaxin, Estrogen
Gluteal muscles sink, tailhead becomes more prominent, sacrosciatic ligament softens
Cortisol levels in the fetus also enhances:
surfactant production (leads to lung maturation)
Expansion of the birth canal is caused by:
Relaxin, estrogens
Maternal behavior prior to parturition is controlled by:
Oxytocin
Which two hormones control milk production in the dam?
Prolactin (synthesis) and oxytocin (letdown/ejection)
Initiation of uterine contractions is caused by:
PGF, oxytocin
Which hormone is responsible for the termination of pregnancy?
PGF
Signs of impending parturition:
Mammary enlargement and colostrum production, Enlargement/elongation and laxity of vulva
Pelvic (sacrosciatic) ligament relaxation and softening of the perineum area, isolation, decrease in appetite (off feed)
Gestation lengths of large animals:
Camelids/mares: 11-12 months
Cattle: 283 days (~9.5 months)
Sheep: 152 days (~5 months)
Goats: 150 days (~5 months)
Pigs: 114 days (3 mo, 3 weeks, 3 days)
First stage of parturition is initiated by:
The fetus
What happens during the first stage of parturition?
Relaxation/Dilation of the cervix, uterine contractions commence, fetus adopts birth posture, chorioallantois enters vagina
What are some clinical signs seen during the first stage of parturition?
Isolation/off feed, colic signs, tail flagging/raising, vaginal discharge, milk & colostrum production (Wax plugs in mares)
What is the ‘Ferguson Reflex’?
Positioning of the fetus so that it triggers a neuroendocrine response in the cervix, resulting in oxytocin synthesis
How does dystocia occur?
Failure of Ferguson Reflex to take effect- fetus does not position itself correctly and does not stimulate the neuroendocrine events in the cervix, preventing full oxytocin production
What happens during the second stage of parturition?
Cervix is completely dilated
Uterine contractions continue (Ferguson Reflex)
Abdominal contractions begin
Fetus enters birth canal –> causing rupture of chorioallantois
Fetus is expelled
What clinical signs are seen during the second stage of parturition?
Water breaks (chorioallantois rupture, lubrication)
Active abdominal contractions
Delivery of fetus
What happens during the third stage of parturition?
Placental circulation is lost
Placental dehiscence and separation occurs
Uterine and abdominal contractions continue
Placental expulsion
What clinical signs are observed during the third stage of parturition?
Expulsion of the placenta!
If you see a placenta hanging from an animal should you pull it to help them pass it?
NO.
How long should stage two (fetal expulsion) last in each species?
Camelid: 5-90 min
Bitch: ~6h
Queen: 30-60 min/kitten (2-4h)
Cow: 30-60 min
Ewe: 30-120 min
Mare: 12-30 min
Sow: 150-180 min (20-30 min b/w piglets)
Best methods for predicting parturition in bitches?
Twice daily rectal temps, look for transient drop (98-97.5)
Ultrasound for fetal gut motility & renal pelvis
P4 levels can help, but not practical
Best methods for predicting parturition in mares?
Milk calcium > 200ppm; foaling in 24-72 hours
Fast decrease in milk pH from slightly alkaline (7.5) to slightly acidic (6.5-6.8); foaling within 24 hours
Best methods for predicting parturition in ruminants?
Breeding dates/physical changes
Size of fetus (U/S v. palpation)
Calving sensors
Drop in rectal temp by 0.5 degrees F at 24 hours before parturition
Other possible (but impractical) tests for predicting parturition in ruminants:
blood glucose, blood progesterone, measurement of sacrosciatic ligament relaxation
Best methods for predicting parturition in sows?
Breeding dates/physical changes
Enlarged mammary glands 1-2 days before farrowing
Restlessness and nesting behavior 12-24 hours prior
Frequent defecation & urination, inc. resp rate
Lie in lateral recumbency last 15-60 min
What is dystocia?
Anything that impedes the process of parturition (can be maternal or fetal causes)
General maternal causes of abortion include:
Failure of expulsive forces
Obstruction of the birth canal
Lack of cervical dilation
Uterine torsion
What are the uterine causes leading to lack of expulsive forces?
Primary & secondary uterine inertia
Uterine damage/rupture
What is primary uterine inertia?
Myometrial defects (overstretching, degeneration, infection, heredity)- Hydrops
Biochemical deficiencies (milk fever/hypocalcemia; pregnancy toxemia/ketosis)
Environmental disturbance (heat/cold stress)
What is secondary uterine inertia?
Consequence of another cause of dystocia (exhaustion); i.e. running out of calcium stores
What is the most common cause of uterine related dystocias?
Secondary uterine inertia
What are abdominal causes leading to lack of expulsive forces?
Inability to strain: age, prepubic tendon rupture, abdominal herniation
What things can lead to a “bony” obstruction of the birth canal?
Bony pelvis: fracture, breed, diet, immaturity, neoplasia, disease
What is the minimum area the pelvic inlet should be for parturition?
150 cm squared
What are some soft tissue abnormalities of the vulva leading to obstruction of the birth canal?
congenital defects, fibrosis, immaturity (heifers)
May require episiotomy or C-section
What are some soft tissue abnormalities of the vagina leading to obstruction of the birth canal?
congenital defect, fibrosis, prolapse, neoplasia, perivaginal abscess, hymen
What are some soft tissue abnormalities of the cervix leading to obstruction of the birth canal?
Congenital defect, fibrosis, failure to dilate
What are some soft tissue abnormalities of the uterus leading to obstruction of the birth canal?
Torsion, deviation, herniation, adhesion, stenosis
What causes lack of cervical dilation? How do we manage these causes?
Ringwomb (sheep) –> CULL
Lack of stimulation (malpositioning of the fetus; prolapse–> manual stimulation)
Adhesions/fibrosis (previous traumas, cull female)
What is Ringwomb?
Heritable condition in sheep
Idiopathic failure of the cervix to dilate
C-section required; cull ewe & do not breed offspring
How do you address a uterine torsion with a closed cervix?
C-section (usually can untwist after delivery)
Rolling or planking cow
How do you address uterine torsion with an open cervix?
Detorsion rod
If detorsion rod fails: C-section
What are fetal causes of dystocia?
Hormone deficiency (failure to initiate birth w/ ACTH/Cortisol; immaturity)
Feto-maternal disproportion
Fetal maldisposition
Fetal death
What are examples of causes of fetomaternal maldisproportion?
Sire genetics
IVF/Cloned calves: large offspring syndrome
Fetal monsters/anomalies: conjoined twins, schistosomus, ankyloses, hydrocephaly
Why does fetal death result in dystocia?
Dead fetus cannot initiate parturition- indicator for inducing!
What clinical signs might be seen if a fetus is dead?
Mummy/macerated fetus
Black vulvar discharge in bitch
Premature placental separation in mares (Red bag delivery)
Reasons for induction of parturition?
Mismating (should be done early)
Prolonged gestation (be 110% SURE!)
Edema of mammary gland (dairy)
Medical necessity (pregnancy toxemia, hydrops)
If likelihood of intervention is high (large fetus, young heifer)
Convenience: planned assistance/attendance
Golden rule for induction of parturition:
Don’t induce!
Let nature run its course
Induction of parturition in cattle:
20-40mg Dexmethasone if beyond 270 days (Calve 24-72 hours; avg 48)
Tighten interval with prostaglandin (Lutalyse, 25mg - 24-48h, abg 36)
Survival good if within 1-2 weeks of due date
Common sequelae of induction of parturition in cattle:
Retained placenta
Oxytocin to expel
Induction of parturition in sheep:
15-20mg Dexamethasone if beyond 137 days (lamb within 36-48 hours)
+/- Prostaglandin
Dinoprost (Lutalyse), 5-10mg; Cloprostenol (Estrumate), 75-100 micrograms/45kg
Survival good if within 1 week of due date
Induction of parturition in goats?
CL DEPENDENT!
Dinoprost/Lutalyse 5-10mg
Cloprostenol/Estrumate 75 micrograms/45 kg
At least 144 days gestation, kid within 30-36 hours
Survival good if within 1 week of due date
If there are concerns for prematurity in goats, before inducing parturition, what should you do?
Give 10-20mg Dexmethasone 6-12 hours before you induce
Induction of parturition in pigs?
CL DEPENDENT!
10-20mg PGF2a (Lutalyse) at least 112-113 days in gestation (farrow in 18-36 hours)
Can give 5-30 IU oxytocin 20 hours AFTER Lutalyse to inc. % to farrow in subsequent 6 hours
What is the stipulation with giving oxytocin IU to sows/gilts for induction?
Higher dose more effective for synchronizing farrowing; BUT
lower doses recommended due to risk of fatigue
Induction of parturition in mares?
Oxytocin IV or IM
10 IU IV q15-30min by slow drip IV
May need 4-6 doses
Min 2 cm dilation of cervix
May then inc. to 20 IU; can go up to 40-60 IU but watch for colic signs
When would be the right time to induce parturition in mares?
ONLY if the mare’s life is in danger
Induction of parturition in bitches/queens?
Difficult, fetal death can result prior to parturition
P4 receptor blocker (Aglepristone) shown effective
Not available in US; no agent to induce queens
How would you determine if an animal is truly overdue?
Know gestation lengths!
Expectancy dates
Owner must be 100% sure of breeding date (be wary, use U/S)
