Pregnancy complication and failure Flashcards
When does pregnancy failure occur?
Early embryonic death: pre-implantation
- before foetal-maternal recognition
- no elongation of CL life
- returns to oestrus
Late embryonic death: peri-implantation
- after CL life has been extended
Abortion: post-implantation
- after organogenesis
Describe how pseudopregnancy occurs after pregnancy loss
Describe how pseudopregnancy occurs in goats
Fertilisation followed by embryonic death:
- CL persists
- accumulation of sterile secretions in uterus
- cloudburst (hydormetra)
Pseudogregnancy occurs in non-mated does at some incidence:
- CL persists
- mechanism unknown
What chromosomal abnormalities can occur possibly leading to embryo loss?
abnormal meiosis
polyspermic fertilisation
failure to extrude 1 or more polar bodies
Fertilisation of oocyte and polar body at first cleavage
Failure of meiosis
What are the causes of embryonic and foetal loss?
Nutrition:
- vitamin A, E deficiency
Environment:
- climate
- stress
- teratogens
- pollutants
Physiological:
- ovulation rate
- uterine environment
Infectious agents
Husbandry/clinical:
- insemination (semen quality, given in error during pregnancy)
- trauma (PD by rectal palpation)
What are the possible routes of infection into the pregnant uterus?
Cervix (ascending infections):
- cervical incompetence
- introduced with sperm (venereal)
Blood (systemic):
- endometrium
- placenta
- fetus
May affect CL
Describe the manifestation of early embryonic death
Tissues usually resorbed and animal returns to oestrus
Describe the manifestation of expulsion of abortus tissue
Death of some fetuses in first half of pregnancy may result in lysis of CL and immediate expulsion
Foetal death after ossification
Describe the manifestation of foetal mummification
Papyraceous mummification: foetal fluids resorbed, foetal membranes shrivelled, uterus contracts
Has no impact on other live foetuses
When are aborted foetuses expelled in a state of autolysis?
species with CL dependent pregnancy
Delay between time of death and lysis of CL
delay in progesterone drop so foetus is maintained in utero and can break down
Pigs, coats, cows (up to 200 days)
When would an aborted fetus be expelled in a fresh state?
CL independent species
foetal death leads to cessation of fetal contribution
placental progesterone declines quick and foetus expelled
ewes, mares
What are SMEDI infections?
Found in the sow
Multiple dead foetuses in different stages of development at time of infection
SMEDI = stillbirths, mummification, embryonic death, infertility
often caused by porcine parvovirus or PRRS virus (porcine reproductive respiratory syndrome)
What are some common infectious agents of abortion in the mare?
Bacterial - cause placentitis:
- streptococcus zooepidemicus
- E. coli
Fungal - cause placentitis:
- aspergillus
Viral - infect placenta and fetus:
- equine herpes virus-1 (EHV-1)
What is the effect of twinning and multiple foetuses in different species?