Sex‐specific fetal weight prediction by ultrasound

Objective To improve sonographic birth‐weight prediction by developing fetal gender‐specific formulae. Methods This was a retrospective cross‐sectional study. Two gender‐specific formulae were produced from the data of 527 patients and the data of a further 349 patients were used to evaluate the formulae. Inclusion criteria were a singleton live fetus, gestational age above 25 weeks, birth weight between 1000 g and 4500 g and fetal biometry within 8 days of delivery. Data retrieval was specifically for the purpose of this study. Results To yield the best‐fit weight formula for each fetal gender we employed step‐wise regression analysis based on fractional polynomials with the biometric parameters biparietal diameter (BPD), head circumference (HC), transverse abdominal diameter (TAD), abdominal circumference (AC) and femur length (FL): estimated fetal weight for girls (g) = − 4035.275 + 1.143 × BPD3 + 1159.878 × AC1/2 + 10.079 × FL3 − 81.277 × FL2 [in cm]; estimated fetal weight for boys (g) = 43576.579 + 1913.853 × log10BPD + 0.01323 × HC3 + 55.532 × AC2 − 13602.664 × AC1/2 − 0.721 × AC3 + 2.31 × FL3 [in cm]. These formulae showed superior results compared with those of conventional weight formulae. Conclusion Gender‐related fetal weight calculation allows optimized prediction of fetal weight at birth. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.