Prevalence of fetal maldispositions in equine referral hospital dystocias.

A retrospective investigation was performed to determine the population characteristics of horses presented for dystocia at 2 equine referral hospitals and the types of fetal maldispositions among these horses. The study population consisted of a similar number of Thoroughbreds (25%), Standardbreds (24%) and draft horses (22%). Most of the current literature pertaining to equine obstetrics is based on a predominately draft horse population (63%). The latter population appeared to have more transverse presentations (P = 0.06), possibly because of the higher number of draft mares. In our study, 43% (6/14) of the transverse presentations occurred in draft breeds. Furthermore, 18% of the draft mare dystocias (6/33) were transverse presentations whereas only 8% (6/73) of the 2 major light breeds (Thoroughbred n = 3; Standardbred n = 3) had transverse presentation dystocias. Despite the significant breed differences between the 2 populations (P < 0.001), the prevalence of all other fetal maldispositions was not different from those previously reported. Severe dystocia was often multifactorial, with 86% of cases involving malposture and over half (58%) of these involving more than one extremity. Head and/or neck deviation were a major reason for referral. In 30% of cases malposition was a factor, and abnormal presentation was involved in 24% of referrals.