Routine ultrasound for detection and management of the small-for-gestational-age fetus.

Serial ultrasound scanning was used routinely in 1687 private patients to detect small-for-gestational-age infants, twins, congenital anomalies, placenta previa, and errors in gestational age estimates. A control population of 8350 private patients was scanned only when indicated. Twenty-three percent of the small-for-gestational-age infants were detected in the control subjects, while routine scanning increased the detection rate to 57% (P = .0007). A high rate of false positive results were found. Seventeen percent of the routinely scanned population were found to be at risk for small-for-gestational age, but only 6% of those actually were small. Despite the increased detection of small-for-gestational-age infants in the routinely scanned population, no significant difference between the routinely scanned and the selectively scanned small-for-gestational-age patients could be shown in the areas of stillborns (6%), neonatal deaths (4%), perinatal mortality (10%), low one-minute (27%) or five-minute (7%) Apgar scores, cesarean section rate (22%), mean gestational age at birth (38.8 weeks), or weight (257 g below the tenth percentile). This occurred despite the aggressive use of maternal bedrest, correction of risk factors, serial scans, nonstress testing, and early delivery when indicated.