Routine ultrasound screening for antenatal detection of intrauterine growth retardation.

This prospective screening program of a large obstetric population was designed to determine the effectiveness of ultrasonic biometry to diagnose intrauterine growth retardation. The results of 3616 pregnancies were analyzed. All pregnancies were dated before the 24th week by ultrasonic measurements. The study compared the effectiveness of three ultrasonic growth parameters: biparietal diameter (BPD), head circumference, and abdominal circumference, to detect intrauterine growth retardation and to determine the optimal gestational age to perform the scan for this purpose. To maintain a high sensitivity required in a screening program, all ultrasonic measurements below the 25th percentile for gestational age were considered abnormal. The predictive value of a positive test in this situation ranged from 0.25 to 0.55, depending on the week of gestation in which the scan was performed. Accuracy of predictions improved greatly when the scans were performed within two weeks of delivery. Abdominal circumference measurements were more predictive of intrauterine growth retardation than either head circumference or BPD measurements or the combination of these parameters. In view of the sensitivity of the test and the prevalence of the disorder, it is concluded that 34 +/- 1 weeks of gestation is the optimal time to screen patients ultrasonically for intrauterine growth retardation.