Embryos

Babies Before they became  furrrr Babies!!!

It is very normal for mares to carry a fetus for 320-380 days. In general 330 days (11 mo) is the most common gestation. Friesians and foals born in Australia tend to be closer to 310-320 range and have healthy viable foals. YOu can also have foals past 340 days that are dis-mature

 (MORE HERE)

Embryo transfers usually are flushed day 4-5 for freezing, 7-8 for direct transfer

5 day - in a dish under a microscope for Embryo transfer, not visible on normal ultrasounds.
(turned into a viable healthy colt!!)


Embryos change size very rapidly from day 12-16 on the ultrasound screen. It's rare to see an embryo before day 14, some are too small, some are in the horns or get lost in folds, 15-17 are the most common scan dates. If you have a mare that is prone to twinning (Tb's are more common) then a day 14 scan with a very trusting vet is suggested followed by a 20 day scan to make sure it was not a double ovulation cycle (can be 1-5 days apart in growth) Up till about day 21/22 you are only looking at the amniotic sac. The white dots on the top or bottom of the image are just the light refraction on a circle called specular reflecors. Uterine tone is a big indicator of pregnancy if you can't visualize a pregnancy before 16 days. Ovaries are only a good indication of pregnancy if you look for a CL (no CL = no pregnancy support). Regular ovulation must occur till 120 days to continue to have a CL support the pregnancy. If your mare has poor CL support Regumate may be required to support a pregnancy. 

from day 20-26 you start to see definition of the actual embryo. The amniotic sac is still black (fluid) and the embryo will start to show white (solid) on the ultrasound.  The sac shape changes from a sphere to an oval then looses it shape. I like to say it starts to look like a fist with the finger/knuckle bumps. 






From 26- 35  you can start to see the embryo develop and the umbilical cord becomes visible. On day 26 you should also be able to see the heart beat!! ❤ Around 30 days the embryo is about 4cm

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around day 36 you start to see shapes of the foal, I like to call it the alien phase because the head and belly are close to the same size. The hart area becomes more pronounced as a black blob (fluid) in the middle of your embryo that is white (solid)

At this phase the embryo is about 5 cm (42 days) growing to about 10 cm by 50 days. It takes up a good portion of the uterine horn.  Endometrial cups are formed around 40 days. If a pregnancy is lost from day 40-120 the eCG (blood pregnancy test) can read a false positive.










You can fetal sex between Days 60 to 70 or between Days 110 to 140. Fetal sexing is virtually impossible between Days 80 to 90 and after Day 140 (over the pelvic rim). Starting on Day 58 of gestation, the genital tubercle will migrate towards the tail to become the clitoris OR will migrate towards the prepuce to become the penis

was born a colt

Around 100-120 days the uterus starts getting pulled towards the head of the mare and the ovaries are pulled closer together by the pull of the embryo weight.
 


After 120 days the placenta takes over the pregnancy management from the ovaries (ovulation occurs during pregnancy) Regumate is usually terminated around 120 days because the placental support. HOWEVER you should get blood tests to make sure because there are a rare few mares that do need to have full term support. ALTHOUGH you should also monitor heart rate and fetal development if keeping a mare on regumage because you can force a mare to carry a dead fetus to term and it can be dangerous for the mare. 

by 150 days the embryo should have fallen over the pelvic rim and be resting in the belly area where it would be hard to ultrasound.