Subconsciously, you’ve been holding your breath for months. From the moment your mare was confirmed in foal, it’s been a tense waiting game. And although she will be foaling soon, you know a healthy foal is still anything but a given. Between breeding and her foaling date lurk a few dozen tragic ways in which she could lose her foal. Whether you call it “slipping a foal” or bluntly label it abortion, it’s a breeder’s most heart-sinking nightmare–and it’s all too common.

Want to dodge the bullet? Knowing what could be a risk for your mare, and being able to recognize the warning signs, is half the battle. Following is a run-down of some of the most common ways in which a pregnancy can go wrong.

Trouble

Nature can terminate a pregnancy for all sorts of reasons. If it happens early in the gestation cycle (in the first 40 days), the tiny embryo is usually expelled through the cervix without notice. According to A.C. Asbury, DVM, Dipl. ACT, Professor Emeritus of the University of Florida and consultant to the Grayson-Jockey Club Research Foundation, an embryo at seven to eight days is only about 0.04 inches (1 mm) in diameter; an embryo at 14 days is about 0.6 inches (15 mm) in diameter. If an embryo this small is slipped, then the owner would likely miss it, he says. Technically, this is called EED, for early embryonic death. EED can be caused by external factors including trauma, stress, or malnutrition; by physiological problems in the mare, such as a hormone deficiency or imbalance or a scarred uterus; by genetic defects in the embryo; or by more than one fetus vying for nutrients. The incidence of EED has been estimated at 5-24%, according to reproductive specialist Jonathan Pycock, BVetMed, PhD, DESM, MRCVS, RCVS, of Equine Reproductive Specialists in Yorkshire, England, and it’s most likely to occur in the interval before pregnancy can be detected by ultrasound (before Day 11). If this is the case, the owner might never know that the mare “caught” at all