The use of a scanner has become fundamental in reproductive work, whether it is getting a mare ready for service or following through after service,  we try to closely line up what we see on the scanner screen to what has been seen in the teasing yards and where the mare is up to in her cycle. In the breeding season a mare is generally in season for 5 days and out of season for approx 16 days. If a mare is thought to be in season, and teasing in the yards we would be looking for a number of things as she comes into the crush - Through rectal examination the vet will be able to feel if the uterus is relaxed,  feel the follicles  (fluid filled capsules that form around the developing ovum) and determine how active the ovaries are - In an inspection of the cervix, if in season,  it will be red, moist and relaxed.  Vets use the scanner to see the size, shape and thickness of the follicle to determine when the mare will ovulate, before ovulation the follicle will change shape and thickness. We would also be looking at the endometrial folds, they are thick when the mare first comes into season and get smaller as she gets closer to ovulation. We also look for any signs of fluid in the uterus, if so this would suggest that she has an infection that needs to be cleared up before service. The aim of the game is to get the mare served as close to ovulation as you can, life of an ovum, post ovulation is 6-8 hours, life of sperm post ejaculation is 48 hours. Re-scanning of the mare two days post service, we are looking for a CL  (Remains of the follicle after ovulation) and looking for any signs of fluid or endometrial folds suggesting that the uterus is dirty. If we are happy with everything, the mare is left in a happy, grass filled environment until 15 days post service, this is the first scan where we will be looking for an embryo. The photo shows a 15 day embryo on the scanner screen, it is usually about 1-2cm. A double check is made that it is a single pregnancy and looks healthy, the mare will then go back out for another 15 days. At 28/30 days post service, we re-scan, this time we are looking for a heart beat on the screen, it shows as a small flutter, also re-checking that it is a single pregnancy. At 45 days post service we do the final scan, checking again for a heartbeat, at this stage you can sometimes see the formation of the foal, such as his head or legs. Considering we are happy with everything we would be finished with the mare and a good result for everyone involved. If at any stage we find that the mare has come back negative, we would short cycle the mare using hormone injections and start the whole process again.