Sovio U, et al. - Researchers compared the ability of estimated fetal weight percentiles estimated using the Hadlock method vs the INTERGROWTH-21st method for predicting extremes of birthweight percentile. They conducted the Pregnancy Outcome Prediction study, a prospective cohort study of blinded serial ultrasonography in nulliparous women with a singleton pregnancy, in Cambridge, United Kingdom. Participants were women who had a research estimated fetal weight performed at 36 weeks’ gestation. Relative to the INTERGROWTH-21st estimated fetal weight percentile, the Hadlock estimated fetal weight percentile performed better at differentiating both small for gestational age birthweight and large for gestational age birthweight. Per findings, they suggest that replacing the Hadlock method by the INTERGROWTH-21st method may result in less effective screening for extremes of birthweight percentile.