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

Objective: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.