Successful management of hydrallantois in a Standardbred mare at term resulting in the birth of a live foal.

A 6-year-old Standardbred mare was presented at 339 days of gestation for investigation of abnormal abdominal distension and ventral edema. Transrectal palpation and ultrasound examination revealed the uterus to be enlarged with an excessive volume of fetal fluid, characteristic of hydrops. Gradual transcervical drainage of 55 L of allantoic fluid over 45 minutes, with concurrent intravenous fluid therapy followed by assisted vaginal delivery, resulted in the birth of a live foal with long-term survival. The birth and long-term survival of a foal from a mare with hydrallantois at term has not been previously reported in horses. However, this report demonstrates that successful outcome for both mare and foal may be achieved in a mare at term with hydrallantois.