The possibility to predict a large infant during pregnancy was assessed using data from a prospective cohort study of 537 singleton pregnancies with term deliveries. Maternal characteristics, symphysis fundal height and ultrasound measurements were used in multivariate analyses for the prediction of an infant with a birthweight of > or = 4,500 or > or = 4,000 g. The positive predictive value was 55% for a birthweight > or = 4,000 g when only maternal characteristics were used, and increased slightly when symphysis fundal height was added. The corresponding value for a single ultrasound measurement at 37 gestational weeks was 52%. Using all available clinical data, positive predictive values of 45 and 80% could be achieved for birthweights of > or = 4,500 and > or = 4,000 g, respectively.