Evaluation of early third-trimester ultrasound screening for intrauterine growth retardation.

Ultrasound fetal biometry is widely used for detection of intrauterine growth retardation (IUGR). Since fetal growth is a dynamic process, studies estimating validity of ultrasound near term may not be applicable earlier in pregnancy. This study applied receiver operating characteristic (ROC) curve analysis to ultrasound biometric data obtained at 26-34 weeks gestation to predict fetuses destined to be IUGR at birth. In this method, the area under the curve (theta) is the index of performance. Sixty-nine (9%) of the 768 singleton infants studied were IUGR at birth. Ultrasound estimated fetal weight (theta = .793) and abdominal circumference (theta = .785) had equivalent performance, significantly better than head circumference (theta = .724) or femur length/abdominal circumference ratio (theta = .619). Performance was not as good as suggested by studies conducted within 2 weeks of delivery.