ET: Pregnancy Placenta Flashcards
Ovary during early pregnancy
Dominant follicle (breed mare within 48 hrs prior to OV)
After OV, 1 CL forms, later 2nd CLs form
Gestation length
Begins day of OV and ends with foaling (11-12 m)
Assessed by ultrasound or TRP
Transit time from ovary to uterus is…
5.5-6 days
Unfertilized ova (UFO)
Retained in the uterine tube
Uterotubal junction blocks UFO from entering the uterus
Significant events during gestation
Maternal recognition of pregnancy
Fixation of the embryonic vesicle / conceptus in the uterus
Attachment of early placenta to the endometrium
Placental maintenance
Transuterine migration (TUM)
Recognition of pregnancy results from successful TUM
Essential for yolk sac to notify the mare is pregnant
Day 16: day of fixation
When does Recognition of pregnancy occur?
Day 12-14
successful ROP measured by blocking PGF release from the endometrium
Primary CL
30 days of progest production
FSH release and follicular waves continue throughout pregnancy
Fetal trophoblasts form endometrial cups
Endometrial cups
Temporary structures, source of eCG/PMSG @ 34 days of gestation (pale, raised, ring formation)
Causes follicles on ovaries to luteinize
Secondary CLs
Second rise in progesterone
What happens after 40-45 days gestation with pregnancy loss?
Its hard to short-cycle her to bring her back into estrus as endometrial cups persist (delay for 3-4 months)
Placental attachment
Between 40-60 days of gestation
70-90 days gestion
Transition from ovarian to uterine/placental maintenance
No longer ovarian dependent
90 to 100+ days of gestation
Pregnancy maintenance uterine/ placental
Ovaries don’t maintain pregnancy
Chronic girdle
Pale, circular area around sphere (location of trophoblast cells)
@ 16 days, comes into contact with uterine horn
Specialized trophoblast cell
Migration @ 34-37 days from CG to endometrium
Methods of pregnancy dx
Teasing
Hormonal evaluation
TRP
TRP and ultrasound
Pregnant mare teasing program
Continue to tease out (reject teaser) during early gestation
Uterine tone ↑, cervix tightly closed
Non pregnant mare teasing program (bred)
Returns to estrus, teases back in, develops a new dominant follicle
Uterine tone ↓ and cervix relaxes (coming into estrus)
Ready to be bred again
Teasing program with more than 50+ days of gestation
Intervals between TRPs ↑ as she passed the time to greatest pregnancy loss
Hormones to dx pregnancy
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)***
TRP uterine and cervical tone for pregnancy dx
Uterine tone ↑ greater than tone @ diestrus
Excellent tone: tubular rigid
Cervix closed and narrow or elongated
By 25 days of pregnancy
Ventral bulge evident
TRP and ultrasound for pregnancy dx (yolk sac)
Size ↑ with time
Distinguish lymphatic cyst from yolk sac within 24 hrs during early pregnancy
Cyst map before breeding
TRP and ultrasound for pregnancy dx (subsequent checks)
Embryo and location within vesicle
Embryo and detection of heartbeat by 25-26 days of gestation
Vesicle shape: round to triangular
Specific concerns (ultrasound)
Small for gestational age (SFGA)
Twins
Vesicle with an abnormal appearance
Confusing pregnancy with lymphatic cysts
Heartbeat absent @ 25 days
Progression of development
Yolk sac → YS diminishes and chorioallantois apparent → fetal trophoblasts migrate from chorionic girdle → endometrial cups form → diffuse attahcment of villi to endometrium
Solutions for confusing pregnancy with lymphatic cysts
Conduct a pre-breeding TRP and US exam
Creating cyst map
Key events mid-gestation
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
Fetal sexing
Early: 70-80 dys
Mid: 120-210 days*
