Reproduction

‘Something just wasn’t right’ 
Pregnancy loss not the end of issues for mare

By Rob Warren

An astute owner realized that something wasn’t right with Lucy, an 18-year-old American Quarter Horse mare, as she neared the end of her pregnancy, but it was the quick response that saved her life.

“Horses start to bloom in their belly and udder later in pregnancy,” said owner Barbara Wilson. “But I noticed Lucy wasn’t developing ‘milk veins’ in her belly and udder toward her due date.”

It was difficult for Ms. Wilson to determine whether something was wrong simply based on Lucy’s size, because the horse had been diagnosed with pituitary pars intermedia dysfunction (PPID) and she was overweight regardless of her pregnancy.

Ms. Wilson contacted Lucy’s primary veterinarian, who performed an ultrasound that showed a non-moving, small fetus—too small for such a late stage in the pregnancy. She immediately referred Lucy to UC Davis Weill College of Veterinary Medicine.

Once at UC Davis, Catherine Renaudin, DVM, DECAR, a health science associate clinical professor, realized the fetus was not viable. “Unfortunately, not all horse pregnancies result in successful births of healthy foals,” stated Dr. Renaudin, the chief of the UC Davis William R. Pritchard Veterinary Medical Teaching Hospital’s Equine Reproduction Service. “Lucy’s case was extremely rare—I have only seen 1 other in my entire career.”

A transrectal ultrasound examination by Drs. Renaudin and Flávia Vieira, DVM, MS, PhD, a resident in equine reproduction, confirmed the presence of a nonviable fetus.

“Based on femur length, we were able to determine that the fetus died in utero at around 100 days of gestation,” Dr. Renaudin said. A full-term pregnancy in a horse is 340 days; Lucy presented to UC Davis at 353 days.

Dr. Renaudin determined age of the fetus based on her prominent research that is known for pioneering and detailing advanced methods for equine fetal ultrasonography, particularly focusing on fetal gender determination, fetal bone development and gestational age, where she has established measurements for the sizes of different parts of a fetus (head, femur, eyes, etc.) throughout pregnancy (Theriogenology. 2024;[15]226:167-172).

Dr. Renaudin has completed tables of these expected measurements for the American Quarter Horse, Warmblood and light breed horses (Reprod Domest Anim. 2025;60[4]:e70059 Link to Reprod Domest Anim.). These tables have proven useful for veterinarians to determine gestational age when it’s unknown and to track proper growth pace when gestational age is known.

Following the extraction of the non-viable fetus, Lucy developed metritis, an infection of the uterine wall. Her bloodwork revealed systemic signs of inflammation and infection, prompting the use of systemic antibiotics and anti-inflammatory medications. Since Lucy was diagnosed with PPID, Drs. Renaudin and Vieira feared the onset of endotoxemia-associated laminitis secondary to metritis, so they initiated preventive laminitis treatments and supportive care. Lucy was transferred to the Equine Internal Medicine Service where Rana Bozorgmanesh, BVetMed, BSc, DACVIM (LAIM), K. Gary Magdesian, DVM, DACVIM, DACVECC, DACVCP, and equine internal medicine resident Mathilde Fournier, DVM, continued her care.

“One of the many advantages of having an animal treated at UC Davis is the collaborative care environment at the hospital,” Dr. Renaudin said. “Various specialty services routinely work together to cover every aspect of a patient’s case, all under 1 roof. Lucy’s case showed the importance of working together with internal medicine specialists and having the unique ability to seamlessly transfer a case in-house for the best continuity of care and safety of the mare.”

Lucy responded well to treatment, showing significant improvement within 48 hours. Drs. Renaudin and Vieira complemented internal medicine’s care by continuing to flush Lucy’s uterus daily until the volume of intrauterine fluid decreased and the fluid collected during each lavage became progressively clearer.

After 6 days in the hospital, Lucy’s care team determined she could return home. At her 2-week recheck appointment, Lucy’s primary veterinarian reported that she was recovering well. She never developed laminitis.

“Even with dedicated owners and appropriate prenatal care, unexpected complications can still occur,” said Dr. Renaudin. “Routine examinations throughout pregnancy, particularly during the last month before term, give us an opportunity to assess fetal presentation and positioning and, when possible, prepare owners for any additional care that may be needed during delivery.” MeV

This story was originally published on the UC Davis website. It was used with permission and edited for style.