Equine Obstetrics Flashcards
describe mare gestation length
average: 340 days
normal range: 320-360d
describe pre-partum changes in the mare
- udder enlargement: 4-6 weeks out
- lactation: 2-14 days out
- colostrum in teats: 24-48 hrs out
- waxing: 6-72 hours
also relaxation of pelvic ligaments (muscles around tail head feel soft and follow) towards the end
describe how milk electrolytes relate to foaling timing
- calcium: <200ppm: 99% NO foaling within 24hrs
- calcium at or greater than 200ppm: 70% will foal within 24 hours and 98% will foal within 72 hours
describe how milk pH relates to foaling timing
- pH >6.4: 99% NO foaling within 24 hours
- pH at or more acidic than 6.4: 56% foaling within 24 hours and 98% foaling within 72 hours
exception: mares with placentitis
-foal is stressed early and signals premature parturition earlier so may see changes in calcium and pH prior to term (viability considered at 300-310 days = earliest can survive outside uterus)
describe normal foaling
- beginning of uterine contractions signals start of stage 1/preparatory phase
- approx 50 min but range 30 min to 6 hours
-nothing to induce release of oxytocin so if bother the mare, she can stop in this phase and wait until she feels safe
-signs: sweating, restlessness, colic, spontaneous milking
-events: uterine contractions, pelvic and cervical relaxation (cervix only opens when membranes and fluids push against it to start dilation), fetal repositioning
-need viable foal for repositioning!! is active movement by foal; if have hypoxia, lose reflexes and foal will not react to uterine contractions by repositioning = bad
- rupture of chorioallantoic membrane signals start of stage 2
-lasts approx 20 min but can range 10-40min - stage 3 begins with fetal expulsion
-avg 60 min but range 15 min to 3 hr
-begin with amnion or fetal parts within 5 min, expect progress every 10 min
-pushing thorax out is big effort, normal for mare to take a break before hips out
-once hips out she’s exhausted so may lay down with legs still in (fine)
-AMNION SHOULD BE WHITE OR BLUEISH AND SHOULD BE ABLE TO SEE FOAL THROUGH MEMBRANE; foal should be able to break but watch and be ready to break for them if they can’t
-also don’t want to happen too fast or GI tract cannot adjust to all this space so often have displaced colon - expulsion of fetal membranes
-if not occur 3 hours post expulsion of fetus, we consider this retained placenta
how does the fetus normally present during expulsion?
anterior longitudinal, dorso-sacral, extended posture
(like a diver/swimmer)
describe dystocia
- prolonged or abnormal parturition
- in 4-10% of mares
-older mares more common (weaker contractions), or emaciated or sick mares (also weaker contractions), mini mares (disproportionate head size), draft mares (baby has more muscle mass)
-but not really a way to predict who will and won’t - most common cause is abnormal posture
-flexure of neck and.or legs is most common
describe consequences of dystocia to the foal
- decreased placental perfusion, placental separation, umbilical cord compression, or inability to expand thorax results in
- fetal asphyxia which leads to
- perinatal death, neonatal disease, or neonatal death
describe the consequences of dystocia to the mare
- trauma and contamination of the genital tract causes
- vagina/cervical adhesions and/or metritis-laminitis-endotoxemia which results in
- decreased fertility in foal heat, increased interval between foalings, and even death
describe red bag
premature placental separation
chorioallantoic membrane and cervical star present
-membrane did NOT break, foal comes out in chorioallantoic membrane
-foal umbilical cord is being compressed, foal is trying to breathe fluids and drowning
-seen typically when placenta thickened, as in placentitis
-need to open membrane immediately and remove foal
when do you consider dystocia?
- no fetal parts or amnion in the vulva within 5 min after rupture of chorioallantois
or
- no progress 10 min after amnion or fetal part in the vulva
or
- abnormal combination of fetal parts in the vulva
when you see soles facing up, what are your two rule outs for abnormal positioning and what is the issue with this?
- anterior presentation, dorsopubic position
- posterior presentation, dorsosacral position
umbilical cord is being compressed! get baby out soon or will die
describe the obstetrical exam for dystocia
- is mare stable
- is cervix dilated
- is birth canal intact
- how is fetus presented
- is fetus alive
- is fetus too big- rare to have disproportion in horses
describe management of dystocia options
- assisted vaginal delivery:
-when mare is conscious
-perform in standing or lateral recumbency, whatever mare decides (some mild xylazine or detomidine)
-for minor correction of posture
-DONT put foaling mare in stocks
-any corrections should be made in uterus (push back in to correct) - controlled vaginal delivery:
-under general anesthesia in dorsal recumbency with elevated hindquarters
-indications: minor corrections of posture or presentation or decreased abdominal contractions by mare - partial fetotomy:
1-2 cuts (if need more than this, likely recommend C-section)
-general anesthesia or epidural if straining
-indications: birth canal in good condition, dead fetus, or flexions - C-section
describe prognosis of dystocia for foal and then for mare
foal:
-survival: if 2 hours, 30%, if 7 hours, 5%
mare: better prognosis so usually choosing mare first unless foal hella valuable
-survival: 80-90%
-if complications: 30%
-foaling rate: 60-80%
