High Risk Pregnancy in the Mare Discussed at Vet Convention

The Table Topic on High Risk Pregnancy in the Mare at the 2009 American Association of Equine Practitioners was very well attended and included several individuals that have published manuscripts on this topic.

The participants were polled to get their input on what types of conditions represent a high risk to successful pregnancy in their practice. An exhaustive list was compiled, including reproductive causes such as placentitis, history of previous complicated pregnancy, twins, torsion, hydrops, umbilical cord or fetal abnormalities, prolonged gestation, premature separation of the placenta, infectious agents (e.g. equine herpesvirus-1, and leptospirosis), abnormal presentation, and an incompetent cervix.

Non-reproductive causes of increased risk to the pregnancy included ventral body wall ruptures, gastrointestinal or respiratory disease, musculoskeletal problems (including laminitis), post-surgical complications (including endotoxemia), and reduced pelvic diameters.

The majority (75%) indicated that placentitis is the major cause of high-risk pregnancy. Identification of mares with placentitis included premature mammary development, vulvar discharge, pelvic ligament relaxation, and history of previous placentitis or previous gross placental pathology. Ultrasonography (transrectal and transabdominal) is the most common diagnostic modality used to confirm the presence of placentitis and monitor the response to treatment. Evaluation of the placenta, fetal fluids, fetal dimensions and posture, and fetal heart rate are key elements to assessment of the fetoplacental unit.

Vaginal or cervical cultures are not routinely done by many of the participants, although there were compelling arguments for performing these more often.

Measurement of serial progesterone and estrogen concentrations is commonly done, and either a precipitous fall or a greater than 50% rise in 48 h signal that delivery might be prior to term.

Treatment for placentitis was discussed briefly. Commonly used antibiotics are trimethoprim sulfamethoxazole, aminoglycosides, and penicillins. The length of treatment in most cases is for the remainder of pregnancy. Flunixin meglumine is used by approximately 50% of practitioners; however, the length of treatment is highly variable, and most veterinarians use it for at least one week. Pentoxifylline is used by one-third of practitioners, the cost of treatment being the predominant reason for not adding it to the treatment regime.

This Table Topic was facilitated by Kristina G. Lu, VMD, Dipl. ACT, of Hagyard Equine Medical Institute, and Sara K. Lyle, DVM, MS, Dipl. ACT, of Louisiana State University.

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