Equine Pregnancy: Physiology and Diagnosis Flashcards
Embryo enters uterus ______ days after ovulation
- 5-6 days
- embryo secretes prostaglandins which stimulate myometrial contractions
Spherical vesicle is very mobile until _____
Day 16
- sticks to base of one horn
Maternal recognition of pregnancy occurs around ______
Days 14-16
Interference with _____ can lead to pregnancy loss
Mobility
Presence of excessive tone in uterus is due to
Elevated progesterone and estrogen produced by the embryo
- keeps early embryo in close apposition to endometrium until attachment
Embryo begins attaching to endometrium at _____
40-45 days
Endometrial cups
Trophoblastic cells invade uterine epithelium around day 40 of gestation
- horseshoe arrangement of pale irregular outgrowths on luminal surface of pregnant horn
Endometrial cup progression
- appear at day 40
- max size at day 70
- regress/sloughed by day 130
- produce eCG
- assist in formation of supplementary CLs and maintenance CLs
Why do we need to know if a mare is pregnant?
- identify open mare
- get mare re-bred
- eliminate twin pregnancy by 14 days
- evaluate pregnancy loss at 15, 30, 42, 60, and 120 days
- for vaccine strategies –> rhino vacc at 5, 7, and 9 mos gestation
What are non-specific indicators of pregnancy?
- behavior assessment
- serum/milk progesterone assay
- vaginal speculum exam
What are specific indicators of pregnancy?
- palpation of repro tract per rectum
- US
- eCG levels
- estrogen in blood, urine, feces
Why use indirect methods
- supports diagnosis of pregnancy
- when other tests are inconclusive
- poor facilities
- vicious or non-domestic equids
- mini’s or ponies
- previous rectal tear
- inexperience of practitioner
Absence of estrus
Mare is teased
- non pregnant mare estrus should be detected 16-19 days after last visible signs of estrus were seen
- failure to return to estrus is suggestive of pregnancy
- not reliable
- 10% of pregnant mares continue to show estrus
Mare may not be pregnant, but shows _______
- early embryonic death following maternal recognition
- prolonged maintenance of CL
- silent estrus
- rarely do mares have lactational anestrus after foal heat
Progesterone testing
High progesterone levels 18-20 days post ovulation implies pregnancy due to functional CL
False positives are frequent
- presence of progesterone does not equal pregnancy
- absence of progesterone equals non pregnancy
Progesterone testing is _____
Non-specific sign of pregnancy
Progesterone only indicates _____
Presence of luteal tissue
Absence of P4 (<1 ng/ml) at 18-20 days is good indication that mare ______
Is not pregnant!
- best way to utilize this hormone is in detecting non-pregnant mares
P4 progression
- secondary CLs elevate P4 levels after 40 days
- P4 declines around 85 days and is negligible by 150-180 days
If the vagina is pregnant, the cervix should be _______
Tight, dry and dull, pale pink and centrally located
Its common to spec a mare at _____ days post ovulation or breeding
18-21 days
Palpation - cervix
16-18 days after ovulation cervix is closed, tight, firm and elongated
- caused by elevated P4
- remains closed until late in gestation
Do you do a vaginal exam to palpate the cervix?
NO, causes abortion
Palpation - uterus
Between 12-25 days gestation uterine wall thickness gradually increases
- uterus becomes tubular, smooth, firm
- tone due to P4 and embryonic factors
- conceptus becomes positioned at base of one horn
- bulge first be palpated around day 20
Palpation - ovaries
- primary CL persists for 160-180 days
- secondary CL form between 40-60 days (can’t palpate these)
- after 120 days, ovaries are difficult to palpate due to fetus pulling them out of reach
Vesicle size
Increases days 20-50, decreases by day 60 and begins descending into abdomen
Ultrasound
Conceptus can first be seen at 9-10 days
- migration occurs until day 16
- guitar pick look at 17-19 days
- embryo proper can be seen at 19 days
- heartbeat seen at 24-25 days
Fetal movement can be seen at _____
40-45 days
Fetal sexing can be performed at _____
62 days
- identify genital tubercle
_____ is used to estimate fetal age
Orbit diameter
Why are mid to late gestation mares difficult to evaluate?
Fetal position
eCG levels
Cups form and begin producing eCG by 30-35 days
- concentration peaks around day 60 and elevates until 120 days
- must know breeding date to obtain sample at best time!
- false neg: sample obtained too early/late
- false pos: fetus dies after cups formed
Estrogen levels
Produced by fetus as early as day 12
- not detectable in blood until after 35 days
- conjugated estrogens elevate after 60 days gestation
- after 150 days estrogens are detectable in urine and feces
- concentrations quickly drop after fetal death
_____ is an indicator of pregnancy and fetal well being
Estrogen levels
