Late-Gestation Pregnancy Monitoring in Mares: Benefits of Ultrasonographic Examination

Once pregnancy is diagnosed at 14-16 days post-ovulation, mares are typically reexamined to confirm fetal viability by detecting a heartbeat after 25 days of gestation. Thereafter, most pregnancies are not monitored unless clinical signs suggest an increased risk of abortion. However, late-pregnancy ultrasonography is extremely valuable for assessing fetal presentation, placental health, fetal growth and development, and fetal well-being. Examination can be performed using both transrectal and transabdominal approaches. If owners can afford only one examination after early confirmation of a viable pregnancy, an ultrasound examination performed after 300 days of gestation is recommended to ensure that the fetus is in cranial presentation and that the placenta is not thickened or separated at the cervical star which can result in premature separation of the placenta ("red bag" delivery).

• To assess fetal presentation using transrectal and transabdominal ultrasonography in late pregnancy and identify abnormal presentations associated with an increased risk of dystocia.
• To assess the placenta using ultrasonography for the early diagnosis of ascending and non-ascending placentitis before the onset of clinical signs, enabling early treatment and improving pregnancy outcomes.
• To assess fetal well-being and development using transrectal and transabdominal ultrasonography.