The effect of breech presentation on the accuracy of estimated fetal weight

To determine whether fetal presentation affects the accuracy of ultrasonographic estimated fetal weight (EFW). This is a retrospective cohort study of singleton pregnancies that underwent ultrasonographic EFW within 3 weeks of delivery at a single institution from 1993 to 2008. Breech presenting fetuses were compared with those presenting cephalic. EFW using the Hadlock formula was compared with actual birth weight (ABW) and reported as mean difference and mean percentage difference. Differences were also considered categorically. Subgroup analyses were performed of women who delivered within 4 days of scan and excluding women with comorbidities. Ability to detect small and large for gestational age infants was compared. Evaluation of 3770 patients, 183 (4.9%) breech presenting and 3587 (95.1%) cephalic presenting revealed no difference in mean gram difference (222.1 g 312.6 vs. 210.7 g 793.2, p = 0.084), respectively, or ability to accurately predict within 10% of ABW (adjusted odds ratio [AOR] 1.23; 95% CI, 0.89,1.69; p = 0.208). Subgroup analyses revealed similar results. There was no difference in the ability to detect small and large for gestational age infants. Presentation does not demonstrably affect the accuracy of ultrasonographic EFW when utilizing the Hadlock formula.