Finding the best formula to predict the fetal weight: comparison of 18 formulas.

Background: To compare the accuracy of 18 formulas in predicting fetal weight and also to make a comparison of these formulas in low-birth-weight fetuses (<2,500 g) and in fetuses weighing >4,000 g.

Methods: Four-hundred-and-ninety-five pregnant patients were enrolled. The estimated fetal weight was calculated using 18 different formulas.