Fetal Death Associated With Premature Mammary Gland Development and Lactation in a Mare Treated With Weekly Injections of Long-Acting Progesterone.

The study reports the case of a pregnant horse with premature mammary gland development and lactation in its seventh month of gestation, treated with long-acting progesterone. The horse, showing no unusual signs except for lack of fetal movement, was found to carry a dead, underdeveloped fetus. An induced abortion was performed which led to the discovery of an enlarged urachus and other minor issues. Post-abortion recovery was normal and the horse was able to successfully give birth in the following breeding season.

Case Presentation

• The study focuses on a 14-year-old pregnant Quarter Horse mare, brought for examination due to premature mammary gland development and lactation.
• Despite being in its seventh month of gestation, the horse did not display any vulvar discharge and vital signs appeared normal.
• The mare had a history of subfertility and was being treated with weekly injections of long-acting progesterone. The last dose was given four days before the examination.

Medical Findings and Procedures

• Upon examination via transrectal palpation and ultrasound, the horse appeared normal with a well-toned uterus and cervix. However, ballottement did not result in notable fetal movement.
• A subsequent transabdominal ultrasound revealed an underdeveloped, immotile fetus with no heartbeat, indicating fetal death.
• An induced abortion was then carried out using repeated doses of cloprostenol. After 54 hours, the mare began labor, leading to the expulsion of the fetus and fetal membranes.
• Post-abortion care included uterine lavage and oxytocin treatment for 48 hours before the horse was discharged to her owners.

Post-Abortion Observations

• The fetus was found to be smaller than expected for its gestational age, with microscopic findings revealing placental stromal mineralization, distended umbilicus adventitia, and dilated umbilical lymphatics.
• The umbilical cord was found to be swollen, with a distended fluid-filled structure surrounding it, which was later identified as the severely dilated urachus.
• The mare recovered well after abortion and had a successful pregnancy the following breeding season, delivering a healthy foal.