Estimate of fetal weight by ultrasound within two weeks of delivery in the detection of fetal macrosomia

© 2014 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Background: Delivery of a macrosomic fetus can be linked with significant maternal and perinatal morbidity. Detection of the macrosomic fetus prior to delivery could have a significant impact on reducing that morbidity. Aims: The purpose of this study was to determine the likelihood of detection of macrosomia at the time of labour and delivery admission using ultrasound. Methods: Retrospective review using the electronic medical record and delivery room logs to identify women admitted to labour and delivery with a birthweight of ≥4000 g. Results: There were 272 macrosomic neonates delivered between January 2010 and December 2012, of which, 91 (33.46%) were identified as macrosomic by ultrasound. Using Spearman correlation, the association between the estimated fetal weight by ultrasound and birthweight was r = 0.214 (95% CI: 0.098-0.325; P = 0.0004). In bivariate analyses, only White race was significant for macrosomia detection with 59 of 149 (39.6%) identified compared with 32 of 123 (26.02%) (P = 0.020) non-White people. In the multivariate model, race remained significant. The odds of being labelled macrosomia for White people was 2.051 (95% CI: 1.188-3.542) compared with non-White people (P = 0.010). Conclusions: Only 33% of fetuses whose birthweight was ≥4000 g were identified by a labour and delivery ultrasound. White race was the only significant factor that increased the odds of having a correct diagnosis of macrosomia by ultrasound.