Cerclage to Manage Cervical Incompetence in Pregnant Mares

Researchers are successfully taking a page from human medicine when it comes to treating one common cause of pregnancy loss in mares: cervical incompetence. Recently, Stefania Bucca, DVM, of the Qatar Racing and Equestrian Club, in Doha, evaluated the efficacy of applying a cervical cerclage suture to affected mares and presented her results at the 2013 American Association of Equine Practitioners' convention, held Dec. 7-11 in Nashville, Tenn.

An incompetent cervix does not relax and open properly during estrus or form a tight seal and close properly during diestrus (when the mare is not in heat). Bucca said that during pregnancy, this failure to close exposes the uterine environment to physical, chemical, or biological challenges and predisposes the mare to developing ascending placentitis (inflammation of the placenta that can cause late-term abortion).

Currently, the standard treatment method involves administering an antimicrobial, a non-steroidal anti-inflammatory, and altrenogest (a progesterone hormone product) for a week's duration at monthly intervals until the foal's birth. "The shortcoming of this treatment is that mares may still have a preterm delivery or fetal loss with histopathological (microscopic) evidence of ascending placentitis despite treatment," Bucca explained.

In women, cervical incompetence can result in preterm birth and late-term abortions, similar to that seen in mares. Human doctors treat this condition by administering progesterone, but they also might perform a cervical cerclage—essentially, stitching up the cervix opening early in pregnancy and removing the sutures near the end of gestation. So Bucca set out to determine how effective and applicable this technique might be for mares.

In her study, Bucca performed six cerclage procedures on four pregnant mares (three Thoroughbreds and one Arabian) with known cervical incompetence. Two mares underwent the procedure during two successive pregnancies. She treated each mare with an antimicrobial and altrenogest for five to seven days after the cerclage and monitored cervical parameters via ultrasound every three to four weeks. Bucca removed the sutures on the mares' estimated due date or right before foaling.

"After cervical cerclage, all mares delivered live foals that survived to at least 1 year of age," she said. "Serial evaluation of the caudal (posterior) reproductive tract did not reveal abnormalities after cerclage sutures were placed. Post-foaling inspection and examination at foal heat were also unremarkable for potential complications."

In conclusion, Bucca suggested performing a cervical cerclage in mares with cervical incompetence that do not respond to altrenogest supplementation. "Although no complications have been reported in association with cervical cerclage, close supervision of treated mares for signs of impending parturition is of critical importance to prevent cervical damage in the case of untimely delivery with the suture still in place," she said.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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