Mares with uncomplicated pregnancies (n = 33) underwent transabdominal sonography to evaluate fetal well-being, obtain measurements of fetal size and characterize the intrauterine environment. Data from the last examination obtained prior to parturition were used for statistical analysis. All mares had one active fetus with good fetal tone. The maximal vertical depth of amniotic fluid (7.9 + 3.5 cm) was less than allantoic (13.4 + 4.4 cm) and fewer echogenic particles were detected in amniotic fluid. The maximal uteroplacental thickness was 1.38 k 0.23 cm (retrospective) and 1.15 ++ 0.24 cm (prospective). In 3 mares small anechoic spaces were imaged between the uterus and placenta. Fetuses had a regular cardiac rhythm with a mean heart rate of 75 2 7 beatslminute and breathing movements. The diameter of the fetal aorta (mean = 22.8 f 2.15 mm) was significantly correlated with neonatal foal weight (P < 0.0008, r = 0.72) and maternal prepartum weight (P < 0.002, r = 0.86). This information on the normal intrauterine environment and fetal well-being can be used to develop a biophysical profile specific for the equine fetus. V e t e r i n q Radiology

Mares with complicated pregnancies (illness, problems at parturition or delivery of an abnormal foal, n = 30) were scanned transabdominally from 298 days gestation to term in order to measure fetal size, evaluate 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 mares produced a normal foal (positive outcome) and 18 mares delivered 19 abnormal foals (negative outcome). Both fetuses that were inactive throughout the entire scan and 4 of 5 fetuses with heart rate abnormalities were abnormal at birth. Three of 4 fetuses surrounded by decreased allantoic fluid quantities had a negative outcome. All mares with large anechoic spaces between the uterus and placenta (n = 3) and/or thickened uteroplacental units (n = 5) delivered abnormal foals. There was a significant correlation between fetal aortic diameter and neonatal foal weight in these complicated pregnancies (P<0.0001, r = 0.85). Fetal aortic diameters were predicted from maternal weight and 6 fetuses had smaller than predicted aortic diameters, all with negative outcomes. A biophysical profile of the equine fetus from 298 days gestational age to term was developed that included 6 factors related to pregnancy outcome: fetal heart rate, fetal aortic diameter, maximal fetal fluid depths, uteroplacental contact, uteroplacental thickness and fetal activity. The profile proved informative about fetal well-being, perinatal morbidity and perinatal mortality. A low score was a definite indication of an impending negative outcome; however, a high score was not assurance of a positive outcome. The utility of such a biophysical profile and future directions for research are discussed.