Equine Pregnancy: Physiology and Diagnosis

Question 1

Embryo enters uterus ______ days after ovulation

Answer 1

5. 5-6 days

- embryo secretes prostaglandins which stimulate myometrial contractions

Question 2

Spherical vesicle is very mobile until _____

Answer 2

Day 16

- sticks to base of one horn

Question 3

Maternal recognition of pregnancy occurs around ______

Answer 3

Days 14-16

Question 4

Interference with _____ can lead to pregnancy loss

Answer 4

Mobility

Question 5

Presence of excessive tone in uterus is due to

Answer 5

Elevated progesterone and estrogen produced by the embryo

- keeps early embryo in close apposition to endometrium until attachment

Question 6

Embryo begins attaching to endometrium at _____

Answer 6

40-45 days

Question 7

Endometrial cups

Answer 7

Trophoblastic cells invade uterine epithelium around day 40 of gestation
- horseshoe arrangement of pale irregular outgrowths on luminal surface of pregnant horn

Question 8

Endometrial cup progression

Answer 8

• 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

Question 9

Why do we need to know if a mare is pregnant?

Answer 9

• 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

Question 10

What are non-specific indicators of pregnancy?

Answer 10

• behavior assessment
• serum/milk progesterone assay
• vaginal speculum exam

Question 11

What are specific indicators of pregnancy?

Answer 11

• palpation of repro tract per rectum
• US
• eCG levels
• estrogen in blood, urine, feces

Question 12

Why use indirect methods

Answer 12

• 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

Question 13

Absence of estrus

Answer 13

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

Question 14

Mare may not be pregnant, but shows _______

Answer 14

• early embryonic death following maternal recognition
• prolonged maintenance of CL
• silent estrus
• rarely do mares have lactational anestrus after foal heat

Question 15

Progesterone testing

Answer 15

High progesterone levels 18-20 days post ovulation implies pregnancy due to functional CL

Question 16

False positives are frequent

Answer 16

• presence of progesterone does not equal pregnancy

- absence of progesterone equals non pregnancy

Question 17

Progesterone testing is _____

Answer 17

Non-specific sign of pregnancy

Question 18

Progesterone only indicates _____

Answer 18

Presence of luteal tissue

Question 19

Absence of P4 (<1 ng/ml) at 18-20 days is good indication that mare ______

Answer 19

Is not pregnant!

- best way to utilize this hormone is in detecting non-pregnant mares

Question 20

P4 progression

Answer 20

• secondary CLs elevate P4 levels after 40 days

- P4 declines around 85 days and is negligible by 150-180 days

Question 21

If the vagina is pregnant, the cervix should be _______

Answer 21

Tight, dry and dull, pale pink and centrally located

Question 22

Its common to spec a mare at _____ days post ovulation or breeding

Answer 22

18-21 days

Question 23

Palpation - cervix

Answer 23

16-18 days after ovulation cervix is closed, tight, firm and elongated

• caused by elevated P4
• remains closed until late in gestation

Question 24

Do you do a vaginal exam to palpate the cervix?

Answer 24

NO, causes abortion

Question 25

Palpation - uterus

Answer 25

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

Question 26

Palpation - ovaries

Answer 26

• 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

Question 27

Vesicle size

Answer 27

Increases days 20-50, decreases by day 60 and begins descending into abdomen

Question 28

Ultrasound

Answer 28

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

Question 29

Fetal movement can be seen at _____

Answer 29

40-45 days

Question 30

Fetal sexing can be performed at _____

Answer 30

62 days

- identify genital tubercle

Question 31

_____ is used to estimate fetal age

Answer 31

Orbit diameter

Question 32

Why are mid to late gestation mares difficult to evaluate?

Answer 32

Fetal position

Question 33

eCG levels

Answer 33

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

Question 34

Estrogen levels

Answer 34

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

Question 35

_____ is an indicator of pregnancy and fetal well being

Answer 35

Estrogen levels