3. pregnancy complictions and failure 1+2 Flashcards
when does pregnancy failure occur
- early embryonic death (pre impantation): before fetal maternal recognition, does not involve elongation of life og CL.
- late embryonic death (peri-implantion): occurs after the life of the CL has been extended
- abortion (post-implantation) after oogenesis
most pregnancy loss occurs very early in gestation
outline why we see reproductive loss in the cow
outline the steps leading to pseudopregnancy following pregnancy loss
what is type 1 pseudopregnancy in the mare and how would you treat it
- early embryonic death after maternal recognition (15 days)
- persistence of CL and prolonged luteal phase
- treat with prostaglanding to lyse CL
what is type 2 pseudopregnancy in the mare
- foetal death after endometial cup formation at 36 days (when the chorionic girdle cells penetrate the uterus and produce endometrial cups that produce eCG)
- lasts until demise of endometrial cups (90-150 days) by the leukocytes
discuss pregnancy loss and pseudopregnancy in the goat
fertilisation followed by embryonic death
- CL persists
- assumulation of sterile secretions in the uterus
- cloudburst/hydrometra (CL persists producing progesterone, cervix closes. sterile secretions in uterus to support fetus that is not there. so secretions build up. by end of gestation period the void of liquid is called cloud burst. hydrometra refers to the stretched uterus containing this fluid
- pseudopregnancy occurs in cyclic non-mated does at the same incidence (CL persists)
- machanism of disturbed luteolysis unknwon
list chromosome abnormalities that occur
may be inherited or arise de novo during gametogenesis, fertilisation and early embryo cleavage
- abnormal meiosis: gametes with unbalanced chromosomes
- polyspermic fertilisation
- failure to extrude 1 or more polar bodies
- fertilisation of oocyte and polar body at first cleavage
- failure of meiosis
list causes of embryonic and foetal loss
- uterine environment (immunological, endorcine, asynchrony)
- environment (climate, stress, teratogens, pollutants)
- infectious agents
- trauma
- insemination (semen quality)
- physiological (ovulation rate)
- nutrition (vit A, E, deficiency)
what is the most common cause of abortion
infection
list routes of infection to the pregnant uterus
- via cervix (ascending infection) due to cervical incompetence (doesnt bar entry) or competent cervix (gets trapped in uterus)
- the blood (systemic) affecting endometrium, placenta or fetus
- pathogens can affect CL (IBR suppresses CL function)
which vanereal pathogens cause infection and early embryonic death in cows
introduced into the repro tract with sperm
bacteria:
- campylobacter fetus var. vanerealis
protozoa:
- tritrichomonas fetus
which venereal pathogens cause infection and early embryonic death in the horse
taylorella equigenitalis
what happens after early embryonic death
tissues usually resorbed and animal returns to oestrus
what happens after embryonic death following infection
pyometra may follow
- in cattle, CL persists, closed cervix and pus accumulation
what happens after abortion of fetus
- during first half of pregnancy may result in lysis of the CL and immediate expulsion
- sometime fetal mummification (fetal fluids resorbed, membranes shrivel, uterus contracts
- in polytocous species mummified fetus will be expelled at parurition with no harm to live fetuses
explain which species abort fresh vs autolytic fetus and why
depends on main source of progesterone
autolysis = fetus broken down
fresh = rapid abortion of the fetus
outline which species most commonly mummify fetuses and when this is more likely to happen
list different outcomes of infection in pregnant sow
- stillbirths
- mummification
- embryonic death
- infertility
reflects the different stages of development at the time of infection
discuss SMEDI conditions
classic SMEDI infection sign:
- full term litter consisting of small mummified fetuses, ranging to full grown stillborn or live weakly piglets
- progressive infection in utero
- abortion rarely occurs
- often caused by procine parvovirus or PRRS virus (less frequently enteroviruses
at what time would we clasify early embryonic death in the mare and how often does this occur
before maternal recognition (<d11)
5-24%
at what time would we classify embryonic death in the mare and how often does this occur
before 40 day gestation (day 14-40)
8-17%
at what time would we classify early fetal death in the mare and how common is this
60-150 day
10%
at what time would we classify late fetal death and how common is it
lafter 150 days
10%
when do we get expulsion of the fetus and placental membranes in the mare and at what time of gestation would we classify stillbirth vs abortion
abortion before 300 days
stillbirth after 300 days
list causes of equine abortion and how common they are
very long umbilicus that can knot and twist
list common infectious agents of abortion in the mare
bacterial: causes placentitis
- streprococcus zooepidemicus
- esterichia coli
- staphylococci
fungal: causes placentitis
- aspergillus
viral: infects placental and fetus
- equine herpesvirus-1
- equine arteritis virus
why is twinning an issue in the mare
reduced surface area for nutrient exchange due to nature of placenta
what are the challenges with twins in the cow
- reduces growth and calf birth weight
- freemartinism in mixed sex pregnancy
what are challenges with multiple lambs
relative placental insufficiency and low birth weight
- set number of caruncles so only so many placentomes
- chorioallantoic placentas are competing for the caruncles
what are the issues with excessively large litter sizes in pigs
uterine crowding
= runts and placental insufficiency
why does equine twinning often result in pregnancy failure
- placenta is epitheliochorial (6 layers)
- conceptus is reliant on nutrition from the entire surface are of the endometrium
- as placentas grow they abut each other and placental interface cannot absorb sufficient nutrients
- as fetus and placenta grow twins run out of toom
- one fetus is resorbed at an early stage OR
- one fetus is mummified at an early stage OR
both twins are aborted, usually at mid to late gestation
discuss twinning int cows
female offspring of dizygotic twins in a mixed sex pregnancy usually in cattle = freemartins
placental fusion permits the exchange of fetal cells and fetal hormones
male hormones androgenize fetus producing a sterile XX/XY chimeric “female”
the female is therefore sterile
- only 10% of female calves that are twins of a male are born normal
regarldess of type of blood mixing, the hormones from the male side interfere with the female embryo
When do a majority of pregnancy losses occur in the cow?
before 21 days
Name 3 physiological reasons that may account for embryonic loss.
- miss the uterine implantation window
- ovulation rate
- infectious agents
- quality of semen
What is the most common cause of abortion in sheep?
infectious agents
How does the predominant source of progesterone affect the speed with which a dead fetus is aborted?
- CL supported pregnancy V. placentla progesterone pregnancy
- placental progesterone pregnancy will beaborted quicker. progesterone will drop quicker in this case
- CL will cause a delay. fetuses will undergo autolysis before abortion occurs
Which species has a high incidence of mummification?
pig
Why is twinning such a problem in the mare?
Due to diffuse placenta relying on surface area. Reduces S/A in twin pregnancies
what is IUGR and its causes in domestic animals and how does it occur
IUGR: intra-uterine growth restriction
impaired growth and development of the mammalian embryo/fetus or its organs during pregnancy
- naturally occuring and environmentally induced IUGR well documented in livestock and litter bearing animals
discuss how the placenta plays a role in intrauterine growth restriction
- multiple fetuses impact on the placents: ruminants = reduced placental blood flow, pig runts = small placenta and reduced blood flow
- placental efficienfy impaired by placental size/weight, uteroplacental blood flow, surface atea
- placental growth altered with nutrition: under and over nutrition
- gynaecological immaturity: breeding at immature bodyweight, moth and fetus compete for nutrients as both growing
discuss nutritional indiced placental growth restriction in adolescent sheep
- ewes themselves are still growing but old enough to establish pregnancy
- the more nutrient that the ewe is given while still growing = the smaller the lamb will be as she uses that nutrition for her own benefit and growth = impacting growth of lamb
list common infectious causes of ovine abortion
- chlamydia abortus
- toxoplasma
- campylobacter
- listeria
- schmallenberg (viral)
discuss schmallenberg virus and how it causes abortion
- late abortion or birth defects in newborn sheep, cattle and goats
- up to 50% malformed lambs reported
- deer, bison and llamas all have antibodies
- mild disease in adults (milk drop, pyrexia, diarrhea)
- transmitted by insect vectors (culicoides sp)
- no evidence of zoonosis
- fetal deformities vary depending on when infection occurred during pregnancy
- mid gestation infection affects CNS development
- if infection is developed 3-5 months cow ppreg or 2-3 months into ewe pregnancy this is when CNS is developing
- malformations may occur in live born cattle and sheep
- no clinical signs where disease is constantly present
- limited vaccines
discuss chlamydial abortion
- main cause of ovine abortion in the UK
- abortion in last 3 weeks of pregnancy
- placental damage from day 90, colonised by bacteria = inflammation
- ability of placenta to support lamb plummets, placenta progesterone development affected
- placenta: thickened areas between cotyledons and brownish exudate over syrface
- organism present in large numbers in abortion products
- contamination of environment and other ewes = importance of removal of abortive products
discuss how toxoplasma gondii causes abortion
- intracellular protozoan (sexual cycle in cats, sheep = intermediate host via ingestion of oocytes in food/water)
- time of infection determines its impact of the fetus
- early pregnancy +++
- mid pregnancy ++
- late pregnancy +
- lesions in brain, liver and kidney of aborted fetus
- infection outcome = resportion, barrenness, mummification, stillbirth, abortion, live lambs
discuss how campylobacter causes abortion
- abortion in last 6 weeks of gestation and the birth of live weak lambs
- spreads rapidly due to organisms in aborted material
- no lesions present in placenta
discuss infectious abortive agents in goats
most agents that cause abortion in sheep are capable of causing abortion in goats
the incubation period for enzootic abortion appears to be shorter in goats than in sheep ( infection and abortion can occur in the same year)
compare bovine BVD infection and gestational age and the outcome of preganancy
discuss causes of non-infectious pregnancy loss in the cow
nutrition
- def. in Vit A, selenium, phosphorous, copper
- negative energy balance
- high intakes of rumen-degradable protein
- dietary oestrogens/anti-oestrogens
stress
- high temps and humidity (fertilisation failure and early embryo mortality)
- other stressors = environment, physiologicalm high milk yield, early lactation
timing of insemination
- too late in oestrus period leads to ovum ageing and embryo death
conception too soon after calving
- high emrbyo loss due to poor uterine environment
list non infectious pregnancy loss in the sow
- failure to establish pregnancy (unattached conceptus susceptible to damage
- failure of established pregnancy (most likely to result from disease
list risk factors of pregnancy loss in the sow
ovulation rate: increased ovulation rate = decreased embryo survival
competition for uterine space: > 5 fetuses = issue
nutrition = high energy levels post service reduces embryo survival
stress: temp/management
list intrapartum factors of fetal death in sow
- litter size: most deaths in last 3rd of litter
- > 20 mins between births
- older sows: > 5 litters = intrapartum death
- weight of sow
- environmental stress (temp, small farrowing crate)
list postpartum factors of fetal death in the pig
- overlaying
- chilling
- lactation < 3 weeks increases piglet mortality
list non infectious causes of pregnancy loss in ewes
- sheep have high fertility rate
- incidence of early embryonic death 20-30 %
- embryonic death associated with multiple conceptions
- sporadic cases of non-infectious abortion (dietary ingestion of phytoestrogens)
- limited structural defects of genital organs
infection = main cause of abortion in sheep
discuss non-infectious pregnancy loss in goats
- habitual abortion in most breeds lows since aborter culled (genetically determined hyperactivity of the maternal adrenal cortex initiating parturition, fetuses dead and oedamtous)
- angora goats have high abortion rates due to high metabolic demand for fibre production (nutritional stress), occuring 90-120 day of gestation
list reasons for pregnancy wastage in the bitch
abortion not considered and clinical problem
- abnormal uterine environment (systic endometrial hyperplasia)
- fetal defects
- progesterone deficiency ( low concentrations at abortion may be consequential)
- infectious agents
list reasons for pregnancy wastage in the queen
progesterone deficiency
