Gender-specific weight estimation of fetuses between 2,501 and 3,999 g--new regression formulae.

Objective: To develop new gender-specific regression formulae to estimate fetal weight focusing on a particular weight range from 2,501 to 3,999 g.

Methods: 3,254 singleton pregnancies were included to generate new regression formulae for female and male fetuses, and to evaluate their accuracy.

Results: In comparison with commonly used formulae, the new gender-specific and weight-range-specific method of fetal weight estimation provided greater accuracy. The mean absolute error was less than 7%.

Conclusions: When properly used, the new formulae can improve the accuracy of weight estimations in fetuses between 2,501 and 3,999 g.