Congratulations, you have successfully bred your mare. But do you have time to sit back, catch your breath, and wait eleven months for the foal? Unfortunately not. You might have cleared the first hurdle, but the obstacle course has just begun. The first two or three weeks after conception is the time to check your mare to see if she is carrying twins. It’s important that you check for twins early in the pregnancy because chances are that if twinning has occurred, the outcome will not be in your favor.

The most common cause of twinning is from double ovulation.

“It’s important to know whether a mare has double ovulated because it’s a signal to look at her closely for twins,” according to Walter Zent, DVM, who does reproductive work for the Hagyard-Davidson-McGee veterinary firm in Lexington.

With today’s technology, you can find out if your mare is carrying twins within a few days of breeding–most can be detected as early as Day 11 or 12. Twins are easily detected until around Day 60, when they develop to a size that the pelvic rim interferes with visualizing the fetuses using rectal ultrasound examination, said Zent. Most veterinarians today have access to ultrasound equipment to scan mares for twins. Although ultrasound has been around for quite some time, it’s only been in the last seven or eight years that it has become routine and affordable for a practitioner to own some of the smaller, portable machines.

With ultrasound, veterinarians will detect nearly 100% of all twins. Before ultrasound, veterinarians performed rectal palpations on mares from 28-30 days onward with decent results. But with the detection rate of ultrasound, it’s better to use it in addition to rectal palpations.

“With rectal palpation alone, four or five sets of undiagnosed twins a year was common,” said Zent. “That’s because 80% of twins in the same uterine horn