equine parturition, dystocia and obstetrics Flashcards Preview

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Flashcards in equine parturition, dystocia and obstetrics Deck (52)
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length of equine gestation


avg: 335 to 342 (11 months)

viable foals delivered from 315 to 400 days

placentitis or anything that stresses baby will cause premature birth

any mare showing signs of premature parturition or prolonged gestation should be examined


physiologic factors affecting gestation length

season of breeding/birth (summer shorter)

mares under light

increased nutrition

older mares have increased incidence of both long and short gestation

sex of fetus-colts longer



pathologic factors affecting gestation length

short: twins, placentitis, other abortigenic infections

long: fescue toxicity 

either: endometrosis (degenerative/fibrotic endometrium)


When is the fetus ready to be birth?

due to activation of the fetal hypothalamus-pituitary-adrenal axis

increased cortisol secretion leads to lung maturation, gut maturation, hepatic glycogen stores, thermoregulate, CNS (stand & move), initiate suckling



when is the fetal HPA axis activated in horses?

last 1-2% of gestation (last 3 to 5 days)



how should you prepare for foaling?

move to foaling location 4-6 weeks prior to expected due date

exposure to local organisms to develop abs (colostrum)


closer observation


predict a foal

measures Ca and Mg

5 indicator squares

more squares changing color

more specific for when she won't give birth


milk electrolyte monitoring

total score of >35 suggests birth within 24 hours

take sample in evening

calcium, sodium, potassium

a low score is a better predictor that the mare won't foal than a high score is that she will foal

less useful in sick mares or those with placentitis


when do mares like to foal?

8 pm to 6 am


mammary secretion pH


when the mare goes under 6.4


foal alert

suture to vulva lips 1-2 weeks before due date

lips part at birth pulling out magnet

alarm signalled

false alarms


final prep

make sure foaling area clean

wrap tail to keep it out of the way

wash perineum and udder

reduce incidence of neonatal infections


positions occupied by the fetus in the last month of gestion

2/3 dorsal recumbency

1/3 left or right lateral



parturition in mare: stage 1

uterine contractions stimulate fetal movement which help put foal in birth position

cervix softens and dilates as chorioallantois and foal wedge into it

ends with rupture of chorioallantois

1 to 6 hours


between stage 1 to 2

1-5 minute window of opportunity immediately after the water breaks and before she is ready to strain to check the foal's positioning and easily correct some malpostures



stage 2 of parturition

about 20 minutes up to 60 minutes

fetus encased in amnion distends cervix and vagina intiating strong uterine and abdominal contractions

amnion visible in 10 mis after water breaks

one foot in advance of other, soles directed down

nose dorsal to legs at level of metacarpus


stage 3 parturition

delivery of fetal membranes (30 min to 3 hrs)



induction of parturition in mares

risky due to uncertain stage of maturation of foal

don't do it unless: very pressing reason

make sure foal is mature enough


criteria for induction

330+ days of gestation

relaxed ligaments

colostrum in udder

milk electrolye changes indicate maturity

relaxed cervix


corticosteroid induction

don't work well-require high dose for several days

risk of dystocia due to malposition/posture

retained placentitis

risk of side effects to mares (laminitis)



prostaglandin induction

takes up to 6 hours

not best

produce powerful contractions, could lead to complications


oxytocin induction

most widely used and method of choice

wide range of doses and routes of administration

best is low dose given IV or IM

once this starts the process it will continue on its own

mare foals within an hour of injection

premature placental separation is fairly common

will work on any mare over 300 days gestation

1st stage prolonged if cervix is not relaxed when inject, could lead to hypoxic foal



1st or 2nd labor is prolonged or porgress is not being made

failure of amnion and/or fetal parts to appear at vulva in timely manner after rupture of chorioallantois

only 1 hoof appears

hooves are upside down

only nose appears

hooves and nose in wrong relative positions


goals for dystocia

live viable foal that isn't in ICU

live healthy reproductively sound mare


causes of dystocia

abnormal disposition



under 40 minutes of stage 2

10% morbidity/mortality


over 40 minutes of stage 2

high morbidity/mortality


After ______________ minutes of stage II labor, every _________ minutes increase in duration

30 minutes

10 minutes

leads to 10% greater risk that fetus will be dead at delivery

16% greater risk that fetus will not survive to discharge from hospital


what happens when the placenta detaches during stage 2 of labor?

foal can become asphixiated

milder cases: hypoxic-ischemic encephalopathy


if mare is not actively straining the placenta may stay attached longer. why?

foal is not engaged in pelvis (transverse/breech maldispositions)

if less assistance has been tried

breed differences: Friesian mares may have slower placental detachment


prevalence of equine dystocia

generally considered<1-4%

higher in maiden mares

some breed dependence (higher in draft horses and minis)



what kinds of dystocia will you see?

malposture of extremities (41%)

normal position and posture but large foal or weak contractions (31%)

malposition-dorsopubic (22%)

hiplock (1%)

redbag (2%)


if head becomes retained, what's the chance of survival?



initial assessment of mare in dystocia

assess general health (ie attitude, MM color, CRT, shock, hemorrhage, dehydration)

perineal area (condition, protrusions, d/c, stinky?, prolapses)

vaginal exam: wrap tail and wash perineum, wash arm, lots of lube 


How to tell if the foal is alive?

anterior presentation-movement, pinch coronary band, slight eyeball pressure, finger in mouth-suck, heartbeat if reach thorax

posterior presentation-pinch coronary band, anal reflex, umbilical vessel pulse


elbow lock (incomplete elbow extension)

muzzle at same level as hoof-fetlock 

hand on chest and repel while applying traction on leg to extend elbow

deliver keeping one hoof in advance of other to minimize cross sectional size of foal


Hurdlers and dog sitters

uni (hurdler) or bi (dogsitter) lateral hip flexion with fetus in anterior presentation

dx: carefully feel under, beside and above fetus back to mare's pelvic inlet

tx: risk of rupturing uterus, anesthetized mare, hoist butt in air and try to repel or fetotomy


fetal oversize

if mild, lots of lube and gentle traction

if doesn't work, C-section, partial fetotomy


foot nape posture

head and front legs in vagina but one or both legs over top of head

risk of rectovaginal fistula or 3rd degree perineal laceration

tx: repel into uterus to get room, correct posture


poll posture

no nose appears following feet, feet may not come out beyond fetlocks

can palpate poll but nose is below pelvi brim

tx: repel fetus and reposition head (rotate in lateral arc then straighten, make sure neck is fully extended before applying traction)


nape posture

extreme version of poll posture

head & neck are ventrally displaced between the forelimbs

hard to reach

tx: fetotomy, C-section, anesthesize mare  and hoist butt


lateral reflection of head & neck

head and neck reflected alongside thorax

often hard to reach far enough to correct

tx: try repelling body and placing snare on heaed to reposition, put one leg into carpal flexion, fetotomy


carpal flexion

unilateral or bilateral

affected carpus usually at pelvic inlet

tx: repel body, grab near fetlock and rotate limb so carpus goes dorsolaterally and flexed fetlock goes medially and limb is extended innto vagina, C-section, fetotomy


Shoulder flexion

uni-swimmer, bilateral-diver

tx: immediate C-section for live foal

manual correction: turn into carpal flexion & correct from there



posterior presentations

hock flexion (25% of posterior dystocias, 90% are bilateral)

hip flexion (50% of posterior dystocias, 94% bilateral)

chance of live foal remote-compression or rupture of umbilical cord leads to asphixia


hock flexion

usually bilateral

tx: repositioning is dangerous (risk of rupturing uterus), C-section, fetotomy



reach in and feel a tail

tx: mutation as dangerous as hock flexio



transverse presentations

ventral more common (all legs presenting), ddx: twins, can sometimes mutate, C-section

Dorsal: C section, fetotomy (hard)



large domed skull-often soft

prevents passage of head or its entry into birth canal

not uncommon in ponies and mini horses

tx: ince with palm knife to collapse, remove top of skull by fetotomy


fetotomy in mares

total fetotomy rarely performed (damage to repro tract)

usually do 1-2 well planned cuts

make all cuts inside uterus, not in cervix or vagina

do not use on a mare in bad condition, do C--section


C-section in mares

not usually done in field

general anesthesia (ventral midline incision)

best option for many: transverse, breech, oversize, dogsitter



treating a mare post dystocia

check uterus for tears

ensure all placenta is passed

check for lacerations/abrasions in cervix and vagina, tx SID with abx/steroid creams to avoid adhesion formation

nasogastric intubation and give mineral oil