The identification of a high-risk pregnancy may be more obvious as in the case of twins or placentitis or it may be difficult in an instance such as placental insufficiency or neonatal asphyxia (oxygen starvation). History is the first place to look for clues, both the past reproductive history and the current events in this mare's life. A past history of foal loss automatically places the mare in a higher risk category than a mare that has had previously uncomplicated pregnancies. Previous uterine infections, twinning, and malpositioning of the foal may develop again. While a previous difficult birth may create complications that effect subsequent pregnancies or foalings, it is not necessarily going to recur or put the mare at risk. It just depends on the nature of the problem. For example, a giant foal creates problems at delivery, but does not create risk for subsequent deliveries unless the mare was injured in the process.

A history of previous foals with failure of passive transfer or sepsis may suggest that the mare does not produce adequate colostrum. In mares that have produced foals with neonatal isoerythrolysis (a condition related to antibodies against the foals red blood cells-RBC), there is a concern that they may also produce antibodies against the RBCs of the current foal that she is carrying. A prior Cesarean section or fetotomy may have damaged the uterus/cervix resulting in a difficult delivery.

Valuable information from the current gestational history is also important in high-risk pregnancy identification. Was there a suspicion of a double ovulation at breeding or twin pregnancy in earlier checks? Has the mare been exposed to equine herpes virus, equine viral arthritis or Ehrlichia risticii (infections that may produce weak or dead foals)? Has the mare been grazing on fescue pasture? Fescue pasture that is infested with an endophyte (fungus) causes prolonged gestation, difficult foaling and agalactia (no milk production) in the mare. Did the mare have endometritis (uterine infections) before she was bred? Has the mare been clinically ill or colicky during her pregnancy? If you answer yes to any of the above questions, then the mare should receive special consideration.