OC12.05: Umbilical artery Doppler indices and ultrasonographic placental biometry in relation to pregnancy outcome in a paradigm of fetal growth restriction

Abstract

Objectives: Nutritional manipulation of pregnant adolescent sheep results in compromised fetoplacental growth and premature delivery of low birthweight lambs. Herein umbilical arterial (UA) Doppler indices and ultrasonographic placental biometry were investigated in relation to pregnancy outcome at term. Methods: Singleton pregnancies to a single sire were established in 14 adolescent ewes and subsequently nutritionally manipulated to generate a wide range of fetal sizes. Fetal biometry, UA Doppler indices and placental index (sum of cross-sectional areas of 10 representative placentomes) were measured by weekly ultrasound between 78.8 and 132.5d gestation. Lamb birthweight and fetal placental (cotyledon) weight were determined following spontaneous delivery near term (145d). Results: One stillborn and 13 live lambs (weighing 1496g–6050g, mean 3485g) were delivered at 132–145d (mean 140d). Birthweight was strongly correlated with placental weight (r=0.901, p=0.001) and was unrelated to baseline fetal biometry at 78.8d. In contrast, placental index at 78.8d was positively correlated with eventual birthweight (r=0.642, p=0.013) and placental weight per se (r=0.637, p=0.026) at term. Placental index correlated with birthweight throughout late gestation (r=0.660–0.712, p=0.004–0.011) but not with placental weight after 108.4d. UA pulsatility index (PI) correlated negatively with birthweight from 95.0d (r=-0.812, p=0.014) and placental weight from 101.3d (r=-0.820, p=0.001) onwards (r=-0.606–0.847, p=<0.001–0.022). Correlations for UA resistance index (r=-0.737–0.868) and systolic:diastolic ratio (r=-0.584–0.842) were similar to PI. Conclusions: Birthweight correlates positively with ultrasonographic assessment of placental size in mid-gestation, prior to slowing of the fetal growth trajectory, and negatively with UA Doppler indices throughout the final third of gestation. Higher Doppler indices and smaller placental size are associated with a greater degree of fetal growth restriction in this experimental paradigm.