Early embryonic loss and twin pregnancy are among the most important causes of reproductive failure in the mare. Early embryonic loss is defined as the loss of gestation during the first 40–45 days of pregnancy and has a multifactorial etiology involving oocyte and embryonic defects, oviductal and endometrial disorders, endocrine dysfunctions, and management-related factors. Its incidence increases markedly with advancing maternal age and may reach very high levels in aged mares. Transrectal ultrasonography allows early diagnosis and facilitates the implementation of preventive measures aimed at optimizing uterine function and pregnancy maintenance.
Twin pregnancy remains one of the leading causes of non-infectious abortion in horses. Early ultrasonographic diagnosis is essential to allow embryonic reduction during the mobile phase of the embryonic vesicles, when success rates are highest. When twin pregnancies are diagnosed after fixation, management becomes more challenging and may require more advanced fetal reduction techniques. This review summarizes the main factors involved in early embryonic loss and discusses current approaches for the diagnosis and management of twin pregnancies in the mare.
