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Caudal or posterior presentation is an uncommon cause of dystocia in the mare. Postural abnormalities of the hindlimbs in conjunction with this presentation can result in major complications (Byron and others 2002). Breech presentation is a specific form of posterior presentation where there is bilateral flexion of the foal's hips. No cases of breech presentation were reported in this paper.
Reports of the incidence of posterior presentation are limited and are mostly from referral cases. Blanchard and others (1989) reported 6 (12 per cent) breech presentations in 50 referrals, Frazer and others (1997) reported caudal presentation in 14 per cent of 141 referrals, and Byron and others (2002) gave an incidence of 9.8 per cent in 161 mostly Thoroughbred (TB) mares referred for dystocia. The incidence in the field is harder to ascertain, although Platt (1979) in a survey of foaling Thoroughbred mares found 98 cases of dystocia of which 3 were posterior presentations. McCue and Ferris (2012) reported only 4 out of 1047 non-referral foalings that were not in cranial presentation. These accounted for 3.8 per cent of dystocias of which only 2 (1.9 per cent) were in caudal presentation (R. A. Ferris, personal communication, Colorado State University). Vanderplassche and others (1972) estimated that 1 in 500 births (0.2 per cent) involved posterior presentation. Also, Ginther and Williams (1996) found no cases of posterior presentation at eight farms in 517 spontaneous Thoroughbred, Standardbred, Quarterhorse and miniature horse births.
Mobility of the fetus in the uterus and the ability to freely rotate to either anterior or posterior presentation persists up to five (Bergfelt and Adams 2011) or eight months (Ginther and others 1994, Bucca and others 2005). However, during late gestation the increasing size of the fetus means that any change in presentation in the uterus becomes increasingly difficult …