Intrauterine growth restriction and Doppler ultrasonography.

To clarify the difference between the fetus that is small for gestational age and the fetus with true intrauterine growth restriction, we undertook a retrospective study of singleton fetuses who had fetal weight estimation and umbilical artery Doppler velocity studies within 2 weeks of their delivery. Fetuses were divided into four categories on the basis of sonographic results from their last examination. Statistical comparisons of neonatal outcome were made for the four groups, which totaled 578 fetuses. Increased cesarean section for fetal distress, stays in the neonatal intensive care unit, and increased neonatal morbidity were seen in both small for gestational age and average for gestational age neonates with abnormal Doppler blood flow. The small for gestational age fetuses with normal Doppler studies showed no increased morbidity when compared with their average for gestational age cohorts. Umbilical artery Doppler blood flow studies were a better predictor of neonatal outcome than estimated fetal weight. Small for gestational age fetuses with normal Doppler studies most likely represent constitutionally small, not pathologically growth restricted, fetuses.