Birth weight percentiles among subsets of stillbirths and live births.

Birth weight for GA at death (stillbirths) or delivery (live births) by the SCRN algorithm [17]. Stillbirths and live births in women with pregestational (type 1 or type 2) or gestational diabetes or with chronic hypertension or gestational hypertension/preeclampsia were excluded from the subset without maternal diabetes. Stillbirths and live births with malformations or chromosomal abnormalities or who were estimated to be aIn this subset, GA was estimated using an expected due date based on an ultrasound examination at ≤20 wk 6 d or last menstrual period that agreed with that ultrasound, and for stillbirths there was an interval of 7 d or fewer between the date the fetus was last recorded alive and the date fetal demise was first reported.bUnadjusted OR for stillbirth for infants with birth weight in the percentile group shown compared to infants in the reference group from a logistic regression model that included effects for percentile group only.The ORs adjusted for stillbirth risk factors as defined in Table 4, footnote b (excluding adjustment for pregestational hypertension and pregestational diabetes in the subset without maternal diabetes or hypertension), were similar and are not shown.cAnalysis weights that accounted for the basic study design plus other aspects of the sampling were used.In the subset of pregnancies without maternal diabetes or hypertension/preeclampsia, unweighted sample sizes were 384 stillbirths and 1,402 live births. In the subset of non-anomalous singletons ≥24 wk gestation, unweighted sample sizes were 315 stillbirths and 1,661 live births. In the subset with optimalestimation of GA, unweighted sample sizes were 199 stillbirths and 1,226 live births.dIndividualized norm percentiles were derived using the fetal weight for GA equation from Bukowski et al. [15].eUltrasound norm percentiles were derived using the fetal weight for GA equation and standard error from Hadlock et al. [19].fAlexander et al. population norm percentiles of birth weight for GA were used [18].Simple linear interpolation was used with the Alexander et al. birth weight percentiles reported for completed weeks of GA in whole weeks to derive birth weight percentiles for GA in weeks and days.LB, live birth; SB, stillbirth.