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?
Why does equine twinning cause pregnancy failure?
What are the possible outcomes of pregnancy loss in twin pregnancies?
one fetus resorbed at early stage
one fetus mummifed at early stage
both twins aborted mid-late gestation
Which animal has the highest incidence of mummification?
Pigs
What is IUGR?
intra-uterine growth restriction
Impaired growth and development of the mammalian embryo/foetus or its organs during pregnancy
What are the causes of intra-uterine growth restriction (IUGR)
maternal or foetal metabolic or homestatic mechanisms
maternal nutrition, nutrient imbalance
Environmental contaminants
Toxic substances
Poor management
Maternal intestinal malabsorption
Insufficiency of uterus endometrium or placenta
Temp and stress
What is the effect of the placenta of IUGR?
multiple fetuses impact placenta e.g., reduced placental blood flow
Placental efficiency impaired by placenta size, uteroplacental blood flow/angiogenesis, surface area
Placental growth altered with nutrition
Gynaecological immaturity - breeding at immature body weight => mother and foetus compete for nutrients
What is the cause of Schmallenberg virus?
late abortion or birth defects in newborn sheep, cattle and goats
Has greatest affect mid gestation when CNS is developing
Usually asymptomatic in adults
What is the main infectious cause of ovine abortion?
Chlamydial abortion
Abortion in last 3 weeks of pregnancy
Placental damage from d90, colonised by bacteria => inflammation
What are the pathological features of chlamydial abortion?
thickened areas of placenta between cotyledons
brownish exudate on surface
Describe the effect of toxoplasma gondii in pregnancy loss in the ewe
Intracellular protozoan
Time of infection determines impact of the foetus
Damage decreases throughout pregnancy
Causes lesions in brain, liver and kidney of foetus
Describe the effect of campylobacter species on abortion
abortion in last 6 weeks of gestation
birth of live weak lambs
spreads rapidly
no lesion in placenta
What are the most common agents that cause abortion in sheep?
Toxoplasma
Chlamydophila
Listeria
Coxiella
Describe the effect of bovine BVD infection in early gestation
Describe the effect of bovine BVD infection in mid gestation
Describe the cause of bovine BVD infection in late gestation
When does foetal immunocompetance develop in cows?
~d125
What are causes of non-infectious pregnancy loss in the cow?
Nutrition:
- Vit A, Se, P, Cu deficiency
- -ve energy balance
Stress:
- high temp and humidity
- high milk yield
Insemination timing:
- too late in oestrus
Conception too soon after calving:
- poor uterine environment
What factors affect risk of pregnancy loss in the sow?
What intrapartum facotrs affect pregnancy loss in the sow?
litter size
> 20 mins between births
Older sow
Weight of sow
Environmental stress
What post-partum factors affect the death of newborns in the sow?
overlaying and chilling
lactation <3 weeks
What is the main cause of abortion in sheep?
infectious agents
What causes abortion in the bitch?
Abnormal uterine environment
Foetal defects
Progesterone deficiency
Infectious agents
