ULTRASONOGRAPHIC ASSESSMENT OF FETAL WELL-BEING DURING LATE-GESTATION- DEVELOPMENT OF AN EQUINE BIOPHYSICAL PROFILE

Mares with complicated pregnancies (illness, problems at parturition o r delivery of an abnormal foal, n = 30) were scanned transabdominally from 298 days gestation to term in order to measure fetal size, evalua te fetal well-being and characterise the intrauterine environment. The results of the last scan obtained prior to parturition were compared to normal data obtained from fetuses of comparable gestational age to develop a biophysical profile specific for the equine fetus. Twelve ma res produced a normal foal (positive outcome) and 18 mares delivered 1 9 abnormal foals (negative outcome). Both fetuses that were inactive t hroughout the entire scan and 4 of 5 fetuses with heart rate abnormali ties were abnormal at birth. Three of 4 fetuses surrounded by decrease d allantoic fluid quantities had a negative outcome. All mares with la rge anechoic spaces between the uterus and placenta (n = 3) and/or thi ckened uteroplacental units (n = 5) delivered abnormal foals. There wa s a significant correlation between fetal aortic diameter and neonatal foal weight in these complicated pregnancies (P <0.0001, r = 0.85). F etal aortic diameters were predicted from maternal weight and 6 fetuse s had smaller than predicted aortic diameters, all with negative outco mes. A biophysical profile of the equine fetus from 298 days gestation al age to term was developed that included 6 factors related to pregna ncy outcome: fetal heart rate, fetal aortic diameter, maximal fetal fl uid depths, uteroplacental contact, uteroplacental thickness and fetal activity. The profile proved informative about fetal well-being, peri natal morbidity and perinatal mortality. A low score was a definite in dication of an impending negative outcome; however, a high score was n ot assurance of a positive outcome. The utility of such a biophysical profile and future directions for research are discussed.