How to tell if my mare is pregnant.

Question
Hi Lisa,
  I took my 7 year old mare to a jack and she got covered on April 21 this year and I was wondering what the first sign of pregnancy is and how I can tell for sure the soonest. I know you can have her ultra sounded of whatever but that expensive and I've also heard about the urine test but how accurate is that? When would her belly start to grow because I noticed that she has grown just in her belly and I just want to make sure to see if I need to take her back or not. She has had a very little amount of blood and fluid that looks like she is in heat but its not the normal amount and she doesn't have any of her other normal signs of being in heat so I don't know and this is her first time so I am trying to make certain that all is well.
                 Thanks,
                     Heather

Answer
Hi Heather,
             The first sign that you will see is that your mare will not come into heat. Most of the development of the foal happens in the final three months of of the pregnancy. Usually, there is no change in the mares body until then. She can be examined with ultrasound Mares should be ultrasounded between 13 and 15 days after ovulation The blood tests can be used between 40 and 100 days after breeding, and rectal palpitation can be used from three months on.

Lisa