Stillbirth and the small fetus: Use of a sex-specific versus a non-sex-specific growth standard

To determine if the use of a sex-specific standard to define small-for-gestational age (SGA) will improve prediction of stillbirth.Study design:We performed a retrospective cohort study of singleton pregnancies excluding anomalies, aneuploidy, undocumented fetal sex or birthweight. SGA was defined as birthweight <10th percentile by the non-sex-specific and sex-specific Alexander standards. The association between SGA and stillbirth using these standards was assessed using logistic regression.Result:Among 57 170 pregnancies meeting inclusion criteria, 319 (0.6%) pregnancies were complicated by stillbirth. The area under the receiver operating characteristic curve for the prediction of stillbirth was greater for the sex-specific compared to the non-sex-specific standard (0.83 vs 0.72, P<0.001).Conclusion:Our findings suggest adoption of a sex-specific standard for diagnosis of SGA as it is more discriminative in identifying the SGA fetus at risk for stillbirth.