Do Serial Sonograms Help Predict Birth Weight?
The estimation of birth weight is an important aspect of decisions about the management of late pregnancy and delivery. Experienced clinicians are able to estimate birth weight within 500 g (1 lb, 1 oz) in 85 percent of average-weight term infants, but this percentage decreases for preterm or macrosomic fetuses. The average error in birth weight predicted by sonogram is estimated to be between 6 and 15 percent. Again, the average error increases in infants weighing less than 2,500 g (5 lb, 8 oz) or more than 4,000 g (8 lb, 11 oz). Several strategies have been advocated to provide the best prediction of birth weight, especially in tiny or unusually large fetuses. Multiple ultrasonographic examinations in late pregnancy have been reported to improve predictions but have significant costs. Pressman and colleagues compared the predictive ability of sonographic examinations early in the third trimester with examinations conducted after 37 weeks’ gestation. They studied healthy singleton pre
