Pregnancy failure Flashcards
When does early embryonic death occur?
— Pre-implantation phase
— Before foetal-maternal recognition
— Does not involve elongation of life of CL
When does late embryonic death occur?
— Peri-implantation phase
— Occurs after the life of the CL has been extended
— Luteotrophic factor has been produced
When does abortion occur?
— Post-implantation phase
— After organogenesis
NOTE: Fertility: relates to ability to conceive and
become pregnant, not pregnancy loss.
Approximately 75% of all reproductive pregnancy wastage occurs before . . . in the cow?
Day 21 with the majority occurring between 8 and 18 days after insemination
How do fetal abnormalities arise?
Abnormalities in meiosis:
— Gametes with unbalanced chromosomes
— These can be fertilised to give abnormal embryo
• Polyspermic fertilisation
• Failure to extrude 1 or more polar bodies
. Fertilisation of oocyte and polar body at
first cleavage
. Failure of meiosis
What are some of the causes of embryonic and foetal loss?
Nutritional
— E.g. Vit A and Vit E deficiency: cows, pigs
Environmental
— Climate (high heat)
— Stress
— teratogens (environmental factors that induce fetal
abnormalities during embryogenesis)
Physiological
— Ovulation rate (increased rate in pigs can effect it)
- Uterine environment
. Asynchrony of uterus, ovary and embryo
• Immunological (mothers immune system must tolerate
allogenic fetus expressing paternal antigens)
• Endocrine (lack of progesterone)
• Failure of maternal recognition of pregnancy
. Infectious agents
What are some husbandry and clinical factors that can induce abortion, conception loss?
• Insemination — Semen quality: .May affect fertilisation/embryo quality — Given in error during early pregnancy . May cause embryo loss . Trauma — PD by rectal palpation after 42 days . <2% loss — Palpation of the uterus . Can cause substantial embryo mortality if performed early in pregnancy
What are common infectious agents of abortion?
. Bacterial
• Parasitic
• Fungal
• Viral
What happens to the fetus after early embryonic death?
Tissues resorbed and animal returns to oestrous if no other conceptus in the uterus. As mentioned previously, if prior to maternal recognition of pregnancy then no delay to cycle.
What happens to the fetus after death following infection?
Pyometra may occur
What happens when there is expulsion of the aborted fetus?
— Death of some (but not all) foetuses during the first half of pregnancy may result in lysis of the CL and
immediate expulsion. Foetal death after ossification
As there has been ossification fetus cannot be resorbed.
What happens to cause fetal mummification?
— Papyraceous mummification: foetal fluids resorbed
foetal membranes shrivelled, uterus contracts
— In polytocous species, mummified foetus expelled at
parturition with no harm to live foetuses
— Develops in multiparous bitch, queen and sow
— Less common in uniparous species
Aborted fetus may be in state of autolysis or fresh depends on speed with which agent dispatches
fetus, and means by which pregnancy maintained. What happens to the species that are CL dependent in pregnancy?
— Pigs, goats
— Cows (up to 200 days)
— There can be a delay between time of death and lysis of CL
Aborted fetus may be in state of autolysis or fresh depends on speed with which agent dispatches
fetus, and means by which pregnancy maintained. What happens to the species that are CL independent in pregnancy?
— Ewes, mares
— Fetal death leads to cessation of fetal contribution.
Because P4 is produced by the placenta.
— Placental progesterone declines
— Fetus expelled in fresh state
. E.g, chlamydial enzootic abortion in ewes
In which species is mummification most common?
Sow
