ET: Pregnancy Placenta

Question 1

Ovary during early pregnancy

Answer 1

Dominant follicle (breed mare within 48 hrs prior to OV)
After OV, 1 CL forms, later 2nd CLs form

Question 2

Gestation length

Answer 2

Begins day of OV and ends with foaling (11-12 m)
Assessed by ultrasound or TRP

Question 3

Transit time from ovary to uterus is…

Answer 3

5.5-6 days

Question 4

Unfertilized ova (UFO)

Answer 4

Retained in the uterine tube
Uterotubal junction blocks UFO from entering the uterus

Question 5

Significant events during gestation

Answer 5

Maternal recognition of pregnancy
Fixation of the embryonic vesicle / conceptus in the uterus
Attachment of early placenta to the endometrium
Placental maintenance

Question 6

Transuterine migration (TUM)

Answer 6

Recognition of pregnancy results from successful TUM
Essential for yolk sac to notify the mare is pregnant
Day 16: day of fixation

Question 7

When does Recognition of pregnancy occur?

Answer 7

Day 12-14
successful ROP measured by blocking PGF release from the endometrium

Question 8

Primary CL

Answer 8

30 days of progest production
FSH release and follicular waves continue throughout pregnancy
Fetal trophoblasts form endometrial cups

Question 9

Endometrial cups

Answer 9

Temporary structures, source of eCG/PMSG @ 34 days of gestation (pale, raised, ring formation)
Causes follicles on ovaries to luteinize

Question 10

Secondary CLs

Answer 10

Second rise in progesterone

Question 11

What happens after 40-45 days gestation with pregnancy loss?

Answer 11

Its hard to short-cycle her to bring her back into estrus as endometrial cups persist (delay for 3-4 months)

Question 12

Placental attachment

Answer 12

Between 40-60 days of gestation

Question 13

70-90 days gestion

Answer 13

Transition from ovarian to uterine/placental maintenance
No longer ovarian dependent

Question 14

90 to 100+ days of gestation

Answer 14

Pregnancy maintenance uterine/ placental
Ovaries don’t maintain pregnancy

Question 15

Chronic girdle

Answer 15

Pale, circular area around sphere (location of trophoblast cells)
@ 16 days, comes into contact with uterine horn

Question 16

Specialized trophoblast cell

Answer 16

Migration @ 34-37 days from CG to endometrium

Question 17

Methods of pregnancy dx

Answer 17

Teasing
Hormonal evaluation
TRP
TRP and ultrasound

Question 18

Pregnant mare teasing program

Answer 18

Continue to tease out (reject teaser) during early gestation
Uterine tone ↑, cervix tightly closed

Question 19

Non pregnant mare teasing program (bred)

Answer 19

Returns to estrus, teases back in, develops a new dominant follicle
Uterine tone ↓ and cervix relaxes (coming into estrus)
Ready to be bred again

Question 20

Teasing program with more than 50+ days of gestation

Answer 20

Intervals between TRPs ↑ as she passed the time to greatest pregnancy loss

Question 21

Hormones to dx pregnancy

Answer 21

P4: primary CL, then secondary CL
eCG: 45-120 days
Total estrogens: feral mares and one way preg dx
Estrogen sulfate: 60 days to term (not readily available)***

Question 22

TRP uterine and cervical tone for pregnancy dx

Answer 22

Uterine tone ↑ greater than tone @ diestrus
Excellent tone: tubular rigid
Cervix closed and narrow or elongated

Question 23

By 25 days of pregnancy

Answer 23

Ventral bulge evident

Question 24

TRP and ultrasound for pregnancy dx (yolk sac)

Answer 24

Size ↑ with time
Distinguish lymphatic cyst from yolk sac within 24 hrs during early pregnancy
Cyst map before breeding

Question 25

TRP and ultrasound for pregnancy dx (subsequent checks)

Answer 25

Embryo and location within vesicle Embryo and detection of heartbeat by 25-26 days of gestation Vesicle shape: round to triangular

Question 26

Specific concerns (ultrasound)

Answer 26

Small for gestational age (SFGA) Twins Vesicle with an abnormal appearance Confusing pregnancy with lymphatic cysts Heartbeat absent @ 25 days

Question 27

Progression of development

Answer 27

Yolk sac → YS diminishes and chorioallantois apparent → fetal trophoblasts migrate from chorionic girdle → endometrial cups form → diffuse attahcment of villi to endometrium

Question 28

Solutions for confusing pregnancy with lymphatic cysts

Answer 28

Conduct a pre-breeding TRP and US exam Creating cyst map

Question 29

Key events mid-gestation

Answer 29

Vigilance against enemies of pregnancy Fetus and uterus out of reach 100 dys+, deep in abdomen until 5-7 months, last trimester back in reach

Question 30

Fetal sexing

Answer 30

Early: 70-80 dys Mid: 120-210 days*