New study reveals that amniotic tissue may hold the key to preventing pregnancy loss in horses.
By Courtney Price, Texas A&M University College of Veterinary Medicine and Biomedical Sciences
BRYAN-COLLEGE STATION, Oct. 1, 2025 — Horse breeding is a time- and resource-intensive process, with the average successful pregnancy often costing thousands of dollars in veterinary care, stud fees and breeding. Because horse pregnancies last almost an entire year, owners and breeders often have to wait a long time to see if their efforts will pay off.
As a result, if a mare has a miscarriage, it can be both a huge disappointment and a lost investment.
That’s why veterinary researchers at Texas A&M University, the University of Kentucky, and the University of Sao Paulo are working to understand how certain bacterial infections can cause miscarriages in horses.
One of the most common causes of miscarriage during the third trimester is ascending placentitis, a condition caused by an infection of Streptococcusequi.
“The bacteria enters the cervix and infects the placenta, which is the main source of oxygen and nutrients for the fetus,” said Dr. Sophia Marchio, a doctoral student at the Texas A&M College of Veterinary Medicine and Biomedical Sciences (VMBS).
“When the placenta gets infected, it alters the hormone and immune system of the mare, sometimes causing a miscarriage or premature delivery,” she said.
While scientists know the cause of the problem, detecting it in its early stages remains a challenge.
“How the bacteria affect specific parts of the placenta has not been well studied,” Marchio said. “With our research, we hope to understand not only how miscarriages happen but also ways to detect problems earlier and even prevent pregnancy loss.”
Mysterious membranes
Miscarriages in horses are a complex problem because different organs and tissues have their own unique reactions to triggers like infections.
In a recent publication, Marchio and her doctoral adviser — assistant professor and head of the VMBS’ Comparative Reproductive Laboratory Dr. Yatta Boakari — discovered that one understudied tissue may play more of a role in miscarriages than previously thought.
“We studied the amniotic membrane, which is a physical barrier and closest placental membrane to the fetus,” Boakari said. “It’s like a protective bubble around the foal that shields them from injury during pregnancy. But we discovered that it’s also involved in the mare’s immune response, so it responds to infection and inflammation.”
While the membrane is one part of a complex system, it could play a key role in helping researchers understand why miscarriages happen.
“This particular equine membrane has never been studied up close using RNA sequencing,” Boakari said. “Before our publication, it wasn’t even known whether it had an immune response. We are the first ones to show that it does using RNA sequencing.”
By Courtney Price, Texas A&M University College of Veterinary Medicine and Biomedical Sciences
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