27: non infectious pregnancy loss Flashcards
what is early embryonic mortality?
loss of conceptus prior to maternal recognition of pregnancy (MRP)
what assumption regarding the mare’s fertility usually follows early embryonic mortality?
exception?
assumption is sub fertility / infertility
except: mares
t/f
after early embryonic mortality, a FM will have regular return to estrus
true
NO MRP occurred so cycles continue as normal
what does the term early embryonic death imply?
embryonic losses that occur prior to time of abortion
late embryonic mortality is defined as what?
embryonic loss btwn MRP and completion of organogenesis
how does late embryonic mortality affect FM return to cycling?
pseudo pregnancy occurs b/c MRP has occurred
irregular return to estrus occurs as a result
what is a resorption?
what is dispelled from the FM?
embryonic (or early fetal) tissues break down and components are dispersed
“flimsy” parts of embryo can be absorbed thru endometrium after embryonic loss
FM may have discharge (this is often inapparent) but no discernible conceptus is expelled
what is mummification?
death of 1 or more fetuses in the absence of ascending bacT infection
fetuses and placentas become dessicated via absorption of fetal fluids
when mummification occurs, what is usually occurring in FM repro tract during this time?
CL present (pseudopregnancy occurs)
cervix NOT dilated
mummification MC occurs in which species?
cattle
swine
Pygmy goats
t/f
PgF2a can be given to cows to resolve cases of mummification
false - some require surgical removal, especially if cow is valuable
what is maceration?
occurs w death of fetus in the presence of bacT infection
macerated fetus may, rarely, be retained w/in uterus
what occurs in FM repro tract when maceration occurs?
luteolysis eventually -> cervical dilation -> additional colonization of fetal tissues by ascending organisms
what species MC experiences maceration?
cattle
what is an abortion?
expulsion or delivery of a fetus, live or dead, that is incapable of life outside of the uterus due to pre maturity
it is NONVIABLE
when does an embryo become a fetus?
once differentiation / organogenesis is complete?
what is late term abortion?
abortion occurring in late gestation or near to term
what is still birth?
offspring born dead or found deceased shortly after birth at term
what is MC reason for still births?
severe hypoxia during parturition
what makes a fetus viable or non viable?
its ability to live outside the FM
at what point can you determine that a fetus is viable?
you cannot - you can say that it is alive but you cannot say it is viable until it shows that it is viable once it is born
what are some non infectious mechanisms of pregnancy loss?
- genetic abnormalities of embryo / fetus
- physiologic stress, including systemic (non repro) illness
- toxins
- placental insufficiency
- endocrine abnormalities
- iatrogenic through administration of abortifacient pharmaceutical cocktail -> intentional or inadvertent
why is the embryonic period relatively tenuous in the mare, especially during her first 35 days of pregnancy?
preg maintenance dep on CL
what is the embryonic mortality rate in the mare?
due to what problems most commonly?
2.5-25%
intrinsic reproductive, extrinsic, embryonic
what are the intrinsic causes to embryonic mortality loss in the mare?
foal heat breeding
endometrial degeneration
progesterone deficiency
how common is progesterone deficiency in the mare, leading to embryonic mortality in the mare?
rare
what is intrinsic embryonic mortality loss in the mare due to (d/t) foal heat breeding issues caused by?
when can it occur relative to MRP?
some loss is to be expected
d/t incomplete involution, residual inflammation when embryo arrives in uterus 5 d post fertilization
loss may occur before or after MRP
what is the condition of endometrial degeneration in the mare?
poor histotroph production - endometrial gland duct constricted by fibrosis - interferes w effective implantation
t/f
endometrial degeneration is age related
somewhat true - somewhat age related by not entirely
does endometrial degeneration in the mare affect pregnancy before or after MRP?
what type of pseudopregnancy occurs?
after MRP
pseudopregnancy type 1
why is some loss during foal heat expected?
less fertile b/c of hospitality of uterine environment - less likely for the embryo to survive the uterus during this time
what are some extrinsic causes of pregnancy loss in the mare?
physiologic “stress”
nutrition
how does physiologic stress cause embryonic mortality in the mare?
lysis of the primary CL
what might cause physiologic stress in a mare?
inc ambient temperature
heavy work
transport
endotoxemia
t/f
nutrition has a significant effect on embryonic mortality in the mare
false
this is unlikely
embryo is small and nutritional needs are very small AND is equipped with its own supply in the yolk sac
what are embryonic or fetal causes of embryonic and early fetal mortality in the mare?
chromosomal abnormalities
poor oocyte quality in mares of advanced age
spontaneous, sporadic chromosomal abnormality
immunogenetic influences
mare stallion incompatibility - RARE
mare-jack breeding - failure to produce endometrial cups
when might placental insufficiency occur in the mare?
what is the result
- body pregnancy
- twinning
abortion
what is body pregnancy in a mare?
what does it cause and when?
embryo implants in abnormal loc in the uterine body
placenta expands into both horns but is relatively insufficient
abortion at 8-9 months
fetus may be alive at delivery but NOT viable
what is the MC diagnosed cause of equine abortion?
what % of cases?
twinning
20-30% of cases
what is the mechanism of twinning that leads to placental insufficiency in mares?
one fetus occupies a uterine horn and the boody and the other only the uterine horn
as the fetus occupying the horn only grows, its demands for o2, waste disposal and nutrients begins to exceed the capacity of its placenta to provide them
how does twinning lead to abortion in mares?
what is the condition of the foals born?
distress of the smaller fetus signals birth so both fetuses are delivered
often one is alive but is not viable and small one is dead
why is a mummy foal sometimes born with twins?
if the distress signal from the smaller fetus is not strong enough, the smaller fetus dies and mummifies and is delivered at term w a live foal
when is abortion of twins signaled in mares?
mid to late gestation
what signal from the stressed fetus of twins in the mare cause endocrinologically?
when does this event normally occur?
dec e2
inc 5a pregnanes
normally occurs at end of gestation - shifted to mid/late gestation
what are the possible outcomes of twinning in mares?
- birth of one live foal and one mummy foal at term
- delivery of 2 live foals in later term abortion -> poor viability
- incredibly rarely, birth of 2 live, viable foals at term
- inc risk for dystocia the later in gestation the abortion occurs and w foals delivered at term
which outcome of twins in the mare is the MC result?
delivery of 2 live foals, neither of which is viable
what complications of the mare’s health are associated w twinning?
- retained fetal membranes -> metritis -> endoeoxemia -> laminitis
- delayed uterine involution, therefore do NOT breed back on foal heat
what are 2 likely causes of embryonic mortality in cattle?
nutrition deficiencies
heat stress
what nutrition deficiencies are associated with embryonic mortality in cattle?
def in Cu, Se, Mn
how does heat stress lead to embryonic mortality in cattle?
cow unable to cool off - malformations in embryo, embryonic death
CL may be susceptible to lysis
what toxins lead to embryonic mortality in cattle?
- endophyte-infected tall fescue
- nitrates
what is the pathogen in endophyte infected tall fescue?
Acremonium coenophialum
what does endophyte infected tall fescue cause in cattle, that leads to embryonic mortality?
before or after MRP?
- significantly lower preg rates if grazing heavily infected grasses
- before or after MRP
how does ergovaline affect pregnancy?
what season is it MC?
- ergot-induced hyperthermia => luteolysis
- MC in mid to late summer
what are some sources of nitrate intoxication?
- nitrate accumulating plants [sudan grass, johnson grass, pigweed]
- drought-damaged corn [green stalks and stubble]
- heavily fertilized pastures
what is the patho-physiology of nitrate intoxication?
- nitrate converted to nitrate in rumen => nitrate enters circulation, oxidizes ferrous (Hb) to ferric iron (MHb) => MHb does NOT bind o2 -> hypoxemia => fetal hypoxia -> stress, death -> triggers abortion
what stage abortions tend to occur in cattle with nitrate intoxication?
late gestation abortions
t/f
nitrate intoxication that causes abortion often causes acute death of the dam
false
low levels of intoxication cause abortion that do NOT kill the dam
what toxins cause systemic maternal compromise?
- cyanogenic sugars from johnson and sudan grass
- pesticides applied to alternative forages being fed due to poor crop performance and drought [soybeans]
- aflatoxins in drought-damaged corn
how does pine needle consumption lead to abortion?
vasoconstriction of caruncular vascular bed - > dec blood flow to placenta - > fetal stress - > peripheral endocrine cascade - > fetus premature delivery / abortion
how much pine needles does a cow need to consume to experience side effects?
a lot….. over 2 kg/day
for 3 days
what compound is the toxin in pine needles?
isocupressic acid
what stage pregnancy loss occurs with pine needle intoxication?
late-term abortions
what is a common management strategy for cattle and pine needle abortion?
- abortions will begin about 2 days after ingestion begins - remove cows - abortions stop 2 days later
- balance cost of grazing/not grazing against the possibility of abortion - calculated risk
what does locoweed cause in cattle [Astragalus and Oxytropis]?
abortion at any stage of gestation, fetal malformations
depends on the stage of gestation during consumption
is locoweed intoxication acute or chronic?
chronic - due to 4-6 wks of ingestion
what compound in locoweed is toxic?
indolizidine alkaloid swainsonine
what is the patho-physiology of locoweed intoxication?
- inc fetal vascular resistance - > cardiac insufficiency -> fluid accummulation -> fetal death -> abortion
what iagrogenic causes of abortion occur in cattle?
- anadvertent administration of PgF2a btwn 1 wk and 3-5 mos of pregnancy
- AI of cows believed to be in heat but that were actually pregnant [depends upon how far into cervical canal insemination was performed]
PG should induce abortion until 5 mos, so why is 3 months the rule?
b/c some failure occurs d/t individual variation and it will cause abortion at 3 mos
so do NOT give PG btwn 1 wk and 3 mos of pregnancy
what is the embryonic loss in does?
why?
20-30%
stress or trauma b/c preg maintenance is solely CL dependent
what causes embryonic loss in small Ru?
- heat stress, trauma - rough handling, shearing of ewes, predator attacks
- extreme maternal malnutrition
- genetic abnormalities of the embryo
- medication administration
- toxins
what medications can cause embryonic loss in small Ru?
- inadvertant PgF2a
- high doses of albendazole
toxins that cause embryonic loss in small Ru?
- phytoestrogesn in plants inc embryonic mortality
- veratrum californucum - teratogenic effects 6
what is the background rate of abortion in small Ru?
less than 5%
what toxins cause embryonic loss in small Ru?
nitrate poisoning
locoweed
what does pregnancy toxemia cause in small Ru?
MC in goat or sheep?
abort in latter / terminal stage of pregnancy: goat more sensitive to this b/c all she requires is luteolysis
less common in sheep b/c also have p4 from placenta so harder to abort sheep than goats
what are non infectious causes of preg loss in sow?
- stress / trauma
- CO poisoning
- inadvertent administration of PgF2a at ANY stage of gestation b/c CL dependent all the way thru pregnancy
non infectious causes of preg loss in the hembra?
- stress / trauma
- medication administration
what medications causes preg loss in hembra?
- exogenous corticosteroids even small amounts in ophthalmic ointment in 2nd half of gestation
- single dose of PgF2a at ANY stage of gestation [b.c CL dep all way thru gestation]
what is the expected rate of pregnancy loss in the bitch by 8 wks of gestation?
11-13%
what are non infectious causes of preg loss in bitch d/t?
- genetic abnormalities [in line breeding]
- hypoluteodism [luteal insufficiency]
- medication administration
how common is hypoluteodism in the bitch?
not common - only a few documented cases
what occurs during hypoluteodism?
- p4 begins to decline abnormally btwn d25-35
- is lower than average by day 35-40
what might supplementation with altrenogest cause in pregnant bitches?
- masculinization of FM fetuses
- cryptorchidism in M puppies
- requires twice weekly p4 measurement and fetal monitoring
what does exogenous corticosteroids cause in pregnant bitches?
abortion
what does chloramphenicol cause in pregnant bitches?
fetal death
what is the typical profile of p4 in pregnant bitch?
p4 rises and peaks at 25 days
t/f
it is commonplace to give a pregnant bitch drugs to help her through her pregnancy
false
it is best to give her no drugs during her pregnancy unless absolutely necessary
what are genetic defects d/t in the offspring of a queen?
inbreeding
what causes embryonic mortality, abortion, congenital malformations in the pregnant queen?
nutritional deficits
vit A
taurine
t/f
avoid giving drugs in the queen during pregnency
true
