A search for the most accurate formula for sonographic weight estimation by fetal sex - a retrospective cohort study

O. Barel, R. Maymon*, U. Barak, N. Smorgick, J. Tovbin, Z. Vaknin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


What's already known about this topic?There is conflicting evidence regarding the influence of fetal sex on the accuracy of fetal weight estimation. Sex-specific formulas were developed in an effort to improve the accuracy of sonographic weight estimation. Although several sex-specific models were evaluated in the literature to date, the comparisons included a relatively small number of patients. So far, no one single model has proven to be a preferred method for estimating fetal weight. What does this study add?This study evaluated over 6500 cases and found a significant effect of fetal sex on the accuracy of sonographic fetal weight estimation. In our research population, we saw that using a combination of two formulas to estimate fetal weight provided significantly more accurate fetal weight estimation. Objective: The aim of this study was to assess the effect of fetal sex on the accuracy of multiple formulas for sonographic estimation fetal weight (SEFW). Methods: The cohort included all singleton live births recorded at a single medical center from January 2004 to September 2011. The accuracy of SEFW was compared between male and female fetuses using 6575 SEFW performed within 3days prior to delivery. Fetal weight was estimated using 27 models. Results: The accuracy of different formulas in predicting birth weight of male and female fetuses was found to be significantly different in almost every accuracy index that was compared (P<0.05). The model by Sabbagha et al. was found to be the most accurate in assessing female fetuses. The most accurate model for male fetuses was a sex-specific formula by Melamed et al. We also found that a combination of the most accurate formula for each sex to one combined sex-specific model increased SEFW accuracy significantly. Conclusion: The accuracy of SEFW is significantly related to fetal sex. The combination of the formulas by Melamed et al. and Sabbagha et al. for male and female fetuses accordingly allowed more accurate SEFW in our research population.

Original languageEnglish
Pages (from-to)1337-1344
Number of pages8
JournalPrenatal Diagnosis
Issue number13
StatePublished - 1 Dec 2014


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