Examination of embryonic death in mares using colour Doppler and B-mode sonography

Embryonic death in mares was studied using colour Doppler sonography and B- mode sonography. The aim of this study was to characterize clinical symptom s for an impending embryonic death. In 6 Trotter mares, who have repeatedly been pregnant, the pregnancies were interrupted with a PGF(2 alpha) analogue (Tiaprost) at Days 15, 25, 30 and 40. Three gestations were studied in each group (Day 30 with 4 gestations) . After the PGF(2 alpha). administration these mares were examined every 8 hours until the conceptuses were removed completely. Control groups, each m ade up of 3 pregnant mares, were examined daily. The size of the conceptus and the embryo/fetus, the thickness of the uterine wall, the embryonic hear t rate and the Resistance Index (RI) of the A. uterina were recorded. The embryonic heart rate could be detected in some cases cit Day 18 and in all cases at Day 20 with colour Doppler sonography. It increased from 97-11 1 beats/min at the first detection to about 167 beats/min at the end of the first month of pregnancy. Thereafter it reached a plateau for nearly a mon th and increased slightly to 176 beats/min at the end of the second month o f pregnancy. The embryos of the treated mares (7 of 10) showed a bradycardi a (64-130 beats/min) before death; 1 had a tachycardia (209 beats/min) and 2 had normal heart rates. Beginning on Day 15, the RI values of the ipsilat eral (pregnant side) uterine artery were lower than those of the contralate ral. In the course of early pregnancy the RI values of uterine arteries dec reased further (P < 0.01). In the mares treated at Day 15 this phenomenon w as not observed. In the mares treated at Day 25, 30 and 40, the difference between the ipsilateral and the contralateral uterine arteries, which was s ignificant at the beginning, disappeared 24-48 hours before embryonic death . From PGF(2<alpha>) administration to embryonic death the treated mares ha d significantly higher RI values on the ipsilateral uterine artery than the untreated mares (P < 0.05). Sonographic characteristics of an impending embryonic death were as follows : the form of the conceptus became irregular and the thickness of the uteri ne wall was the same all around the embryonic vesicle. The endometrium beca me heterogen and estrous-like. A reduced volume of conceptual fluids, a str ongly increased echogenity of the conceptual fluids and a disorganization o f the conceptual membranes were the most important criteria after embryonic death. This study shows that colour Doppler sonography is a useful method to diagn ose and predict embryonic mortality in mares. Compared to B-mode sonography , embryonic mortality can be detected earlier and more reliable with the co lour Doppler technique.