Mare might be pregnant

Question
I just have a question regarding ultrasounds. My mare was bred around March 26th, the vet came out approximately 14 to 18 days later. At the beginning of the ultrasound she immediately said yes she is pregnant and she showed me the black round sac and explained what it is, so she had it in sight for about a minute or so.  She went on to check the rest of the uterus and when she attempted to find the sac again she could not find it. She said she would then have to say she is not pregnant, but that she does miss and not to be surprised it I need her to come back in the spring to palpate her or if we end up with a foal.  I was just curious how often this happens and why if she is in foal we could not find the sac again?  Thanks so much!

Answer
Hi Brandy,

It is quite common for a vet to miss a pregnancy on ultrasound between 14-18 days.  Sometimes the "sac" they see can actually be fluid, air or a cyst.  If it were a cyst or an embryonic sac, she should have been able to find it again as a sac would be attached to the uterus and not floating around.

But this doesn't mean that she isn't pregnant.  I had one of my mares ultrasounded at 16 days and the vet stated she was not pregnant but she had a foal the following year!

If you want to know sooner than waiting til next spring to have her checked again, you should have her palpated at about 40 days.  At 40 days, a vet is usually able to verify for sure whether or not the mare is pregnant.

Best of luck,
Sandy