Broodmare C-Section: Subsequent Fertility and Foaling Rates (AAEP 2009)

Cesarean sections, or C-sections, are performed on approximately 15%-25% of pregnant mares admitted to equine hospitals for dystocia (difficult or abnormal labor or delivery). C-sections are also performed as elective procedures or in cases where underlying medical or surgical conditions exist.

AAEP

Dr. Kim Abernathy talks about C-sections in mares.
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"At present, only limited data regarding foaling rates post-cesarean exist. In 1990, Dr. Juzwiak reported a 36% foaling rate in 16 of 19 mares, and in 2002 Dr. Byron reported a cumulative foaling rate of 72% in 26 mares after dystocia was resolved by C-section. Neither of these studies followed fertility rates in a large group of mares for a three-year period of time," relayed Kimberly K. Abernathy, DVM, during a presentation at the 2009 American Association of Equine Practitioners (AAEP) Convention.

To better establish the impact of C-sections on fertility and foaling rates in mares, Abernathy and colleagues reviewed the medical records from 97 mares that underwent C-sections between 1986 and 2000. The collected data included mare age, time between rupture of chorioallantois (fetal membrane) and delivery, postpartum complications, mare and foal survival to time of hospital discharge, and cumulative foaling rates both prior to the C-section and for the three-year period subsequent to the C-section.

"Our study found that both length of dystocia and age of the mare had a negative effect on the foaling rates in the three-year period post C-section," said Abernathy.

Specifically, the researchers found:

  • The cumulative foaling rate prior to C-section was 79%, but it was only 40.5%, 61.3%, and 58.5% in the first three years after surgery;
  • In mares older than 16 years of age foaling rates were only 30% post-surgically;
  • Mean foaling rate post-cesarean was 51% for mares who delivered foals greater than 90 minutes after rupture of the chorioallantois, and 73% if the foals were delivered in less than 90 minutes; and
  • Foal survival was markedly lower in dystocia cases (26%), as compared to medical/surgical C-sections (50%) and elective C-sections (83%).

According to Abernathy, et al., "Acceptable foaling rates can be achieved if a mare is less than 16 years of age and if labor is not prolonged."

This research was performed at Rood & Riddle Equine Hospital in Lexington, Ky. Abernathy is currently practicing at Kentucky Lake Equine Hospital in Benton, Ky.

Co-authors on the study from Rood & Riddle Equine Hospital were Michelle M. LeBlanc, DVM, Dipl. ACVT; Rolf M. Embertson, DVM, Dipl. ACVS; and Scott W. Pierce, DVM. Statistical analyses were performed by Arnold Stromberg, PhD, of the University of Kentucky.

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

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