equine parturition, dystocia and obstetrics

Question 1

length of equine gestation

Answer 1

variable

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

Question 2

physiologic factors affecting gestation length

Answer 2

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

sire

Question 3

pathologic factors affecting gestation length

Answer 3

short: twins, placentitis, other abortigenic infections
long: fescue toxicity
either: endometrosis (degenerative/fibrotic endometrium)

Question 4

When is the fetus ready to be birth?

Answer 4

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

Question 5

when is the fetal HPA axis activated in horses?

Answer 5

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

Question 6

how should you prepare for foaling?

Answer 6

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

exposure to local organisms to develop abs (colostrum)

vaccinate-colostrum

closer observation

Question 7

predict a foal

Answer 7

measures Ca and Mg

5 indicator squares

more squares changing color

more specific for when she won’t give birth

Question 8

milk electrolyte monitoring

Answer 8

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

Question 9

when do mares like to foal?

Answer 9

8 pm to 6 am

Question 10

mammary secretion pH

Answer 10

<6.4

when the mare goes under 6.4

Question 11

foal alert

Answer 11

suture to vulva lips 1-2 weeks before due date

lips part at birth pulling out magnet

alarm signalled

false alarms

Question 12

final prep

Answer 12

make sure foaling area clean

wrap tail to keep it out of the way

wash perineum and udder

reduce incidence of neonatal infections

Question 13

positions occupied by the fetus in the last month of gestion

Answer 13

2/3 dorsal recumbency

1/3 left or right lateral

Question 14

parturition in mare: stage 1

Answer 14

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

Question 15

between stage 1 to 2

Answer 15

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

Question 16

stage 2 of parturition

Answer 16

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

Question 17

stage 3 parturition

Answer 17

delivery of fetal membranes (30 min to 3 hrs)

Question 18

induction of parturition in mares

Answer 18

risky due to uncertain stage of maturation of foal

don’t do it unless: very pressing reason

make sure foal is mature enough

Question 19

criteria for induction

Answer 19

330+ days of gestation

relaxed ligaments

colostrum in udder

milk electrolye changes indicate maturity

relaxed cervix

Question 20

corticosteroid induction

Answer 20

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)

Question 21

prostaglandin induction

Answer 21

takes up to 6 hours

not best

produce powerful contractions, could lead to complications

Question 22

oxytocin induction

Answer 22

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

Question 23

dystocia

Answer 23

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

Question 24

goals for dystocia

Answer 24

live viable foal that isn’t in ICU

live healthy reproductively sound mare

Question 25

causes of dystocia

Answer 25

abnormal disposition presentationposture

Question 26

under 40 minutes of stage 2

Answer 26

10% morbidity/mortality

Question 27

over 40 minutes of stage 2

Answer 27

high morbidity/mortality

Question 28

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

Answer 28

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

Question 29

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

Answer 29

foal can become asphixiated milder cases: hypoxic-ischemic encephalopathy

Question 30

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

Answer 30

foal is not engaged in pelvis (transverse/breech maldispositions) if less assistance has been tried breed differences: Friesian mares may have slower placental detachment

Question 31

prevalence of equine dystocia

Answer 31

generally considered\<1-4% higher in maiden mares some breed dependence (higher in draft horses and minis)

Question 32

what kinds of dystocia will you see?

Answer 32

malposture of extremities (41%) normal position and posture but large foal or weak contractions (31%) malposition-dorsopubic (22%) hiplock (1%) redbag (2%)

Question 33

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

Answer 33

25%

Question 34

initial assessment of mare in dystocia

Answer 34

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

Question 35

How to tell if the foal is alive?

Answer 35

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

Question 36

elbow lock (incomplete elbow extension)

Answer 36

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

Question 37

Hurdlers and dog sitters

Answer 37

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

Question 38

fetal oversize

Answer 38

if mild, lots of lube and gentle traction if doesn't work, C-section, partial fetotomy

Question 39

foot nape posture

Answer 39

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

Question 40

poll posture

Answer 40

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)

Question 41

nape posture

Answer 41

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

Question 42

lateral reflection of head & neck

Answer 42

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

Question 43

carpal flexion

Answer 43

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

Question 44

Shoulder flexion

Answer 44

uni-swimmer, bilateral-diver tx: immediate C-section for live foal manual correction: turn into carpal flexion & correct from there fetotomy

Question 45

posterior presentations

Answer 45

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

Question 46

hock flexion

Answer 46

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

Question 47

breech

Answer 47

reach in and feel a tail tx: mutation as dangerous as hock flexio fetotomy

Question 48

transverse presentations

Answer 48

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

Question 49

hydrocephalus

Answer 49

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

Question 50

fetotomy in mares

Answer 50

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

Question 51

C-section in mares

Answer 51

not usually done in field general anesthesia (ventral midline incision) best option for many: transverse, breech, oversize, dogsitter $$$

Question 52

treating a mare post dystocia

Answer 52

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