Maintenance of Pregnancy Flashcards
Pregnancy failure (the three types + their
Even after successful fertilisation, pregnancies are at significant risk of failure (i.e. fetal loss) Risk of fetal loss tends to decrease over gestation
- Early embryonic loss = loss prior to or around implantation, high risk
- Abortion = post implantation, fetus unlikely to survive birth, moderate risk
- Still birth = fetal death at an age likely to survive birth, low risk
When fetal loss occurs is important – will change the signs, female re-breeding potential and possible complications
What are some physiological processes that might cause fetal loss if interrupted, incomplete or absent? (5)
Luteolysis (PGF2a injection)
Lack of progesterone (P4)
Placental disruption (e.g. umbilical torsion = stops blood supplyàhypoxia) Trauma, Malnutrition, Stress
Failed maternal recognition (luteolysis will occur)
Pathogen or genetic abnormalities that interfere with tissue differentiation in fetus
Outcomes of fetal loss
Embryonic and early fetal loss
- Outcome: conceptus typically resorbed by the uterus, leaving little or no indication
- Signs: may have limited signs if peri-implantation, may occur before preg diagnosis,
long cycle, loss of previous fetal signs Abortion
- Outcome: expulsion (fresh or autolysed fetus) or retention in utero (mummification or maceration)
- Maceration rare and from disease
- Signs: return to estrus, regression of fetal signs, no signs of impending parturition
Expected rates of fetal loss
The majority of fetal loss occurs early in pregnancy )i.e. peri-implantation), with moderate loss in the first half of gestation and few losses late in gestation
*lots of pregnancies fail at implantation
For litter bearing species, loss can be only some or all fetuses depending on cause
Higher than expected abortion rates in a group of animals is called an abortion storm
Common infectious causes of fetal loss
Common non- infectious causes of fetal loss (7)
What might you investigate in the case of abortion? (4)
Look at placenta & aborted fetus
Plants in paddock (i.e. fireweed)
Nutrition
Hormonal profile of mother, and health of mother Infection, disease
Strategies for preventing fetal loss
Until we understand more about the causes of early embryonic loss, its very difficult to prevent and remains a major source of reproductive ‘wastage’
In late summer a flock of ewes, grazing on ryegrass pasture, has an abortion rate of 10% during late gestation, the ewes have no other clinical signs. They were recently
shorn on farm
Is this cause for concern, and if so, what would be a likely issue.
Yes, E
Not, B, because high temp only effects early embryo loss
Pregnancy termination
Typical indicators of termination include:
- Maternal risk (e.g. very young maternal age, laminitis)
- Abnormal pregnancy (e.g. congenital abnormalities, mummification) - Multiple gestation (e.g. twins, triplets etc.)
- Production efficiency (e.g. feedlot heifers)
- Convenience (e.g. accidental mating, unwanting pregnancy)
Physiology of pregnancy termination (days different)
Keeping an eye on pregnancy
Tools exist to diagnose and monitor pregnancy- they may not always be the same. Diagnosis
- Major focus in production animals
- Diagnosis of multiples may be important (e.g. mare, ewe) Monitoring
- More common in mare, bitch, queen
- Often focused on tracking fetal growth & identifying complications
- Maternal health/body condition also assessed
- Towards end of gestation, looking for indicators of parturition.
Pregnancy diagnosis
Pregnancy monitoring
Materinal monitoring
- Circulating P4 conc, body condition, feed intake, weight gain, mammary development Fetal monitoring
- Litter size, fetal viability/distress (HR, movement), Crown rump length, Fetal sexing
- Most ultrasound & x-ray
