Transrectal ultrasonographic measurements of the combined thickness of the uterus and placenta in Spanish Purebred mares

The present study was conducted to establish the normal values of the combined thickness of the uterus and placenta (CTUP) in Spanish Purebred mares during late pregnancy. A total of 107 mares were examined at 210, 240, 270 and 300 days of gestation, of which 13 had abnormal gestations (foetal death, abortion or stillbirth). In mares with healthy foals, CTUP measurements showed significant differences (P < 0.0001) at the various gestational ages (4.83 +/- 0.59 mm, 6.12 +/- 0.60 mm, 7.41 +/- 0.61 mm and 10.45 +/- 0.92 mm at 210, 240, 270 and 300 days, respectively). A high positive correlation was observed between CTUP and gestational age (r = 0.923; P < 0.001). In mares with abnormal gestation, CTUP measurements were significantly (P < 0.0001) higher than in healthy gestations at day 270 (8.89 vs. 7.41 mm) and day 300 (14.17 vs. 10.45 mm). The age of the mare, fertilization time, type of semen and gestation length did not affect the CTUP. The results obtained suggest that the cut-off point for detecting abnormal pregnancies in Spanish Purebred mares is 7.75 mm on day 270 and 12.7 mm on day 300. The authors find that the incidence of placental thickness enlargement in the late gestation of Spanish Purebred is 14%, and a transrectal ultrasonographic examination is highly advisable at 270 days of gestation. Such timely placental assessment could reveal otherwise undetected disorders, thereby enabling early and proper treatments to be administered to prevent foetal loss.