Defining altered fetal growth by second-trimester sonography.

A method of predicting birth weight from a single ultrasound examination between 18-28 weeks' gestation was evaluated prospectively in 315 obstetric patients with singleton pregnancies. Estimated fetal weight at the time of the ultrasound examination was used to predict actual birth weight. At delivery, the percent difference between the projected and actual birth weights was then used to define whether an infant was small, appropriate, or large for gestational age. This method appeared to be accurate and showed identical relationships to the presence of abnormal fetal heart rate patterns in growth-retarded infants as did the traditional birth-weight-for-gestational-age method of defining intrauterine growth retardation.