Birth weight percentiles among stillbirths and live births using different equations to estimate individualized expected weight.

Birth weight for GA at death (stillbirths) or delivery (live births) by the SCRN algorithm [17]. Percentages may add to slightly more or less than 100% because of rounding.aUnadjusted 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.bAdjusted 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 in addition to the percentile group indicators included study site number; paternal age (Table 1 or as noted): maternal age (cAnalysis weights that accounted for the basic study design plus other aspects of the sampling were used.Unweighted sample sizes were 527 stillbirths and 1,821 live births. Unweighted (weighted) sample sizes included in computation of adjusted ORs were 452 (451) stillbirths and 1,665 (1,261) live births.dIndividualized norm percentiles were derived using the fetal weight equation from Bukowski et al. [15].All 19 variables were used in the fetal equation here. (Fetal heart rate was included in the original Bukowski equation but was not collected by the SCRN study. GA in days minus 280 d drops out of the equation when predicting birth weight at 280 d.)eIndividualized norm percentiles were derived using the subset of 11 variables largely non-missing in the SCRN cohort in the fetal weight equation to predict term birth weight: maternal weight, height, race/ethnicity, education, marital status, number of prior term pregnancies, number of prior abortions, altitude of residence, use of ovulation induction to become pregnant, cigarettes smoked per day during the first trimester, and male fetus.fIndividualized norm percentiles were derived using the subset of six variables suggested by Gardosi et al. [20] in the fetal weight equation to predict term birth weight (excluding GA, which drops out): maternal weight, height, race/ethnicity, number of prior term pregnancies, cigarettes smoked per day during the first trimester, and male fetus.gIndividualized norm percentiles were derived using a subset of five variables (the six variables above minus number of cigarettes smoked) in the fetal weight equation to predict term birth weight: maternal weight, height, race/ethnicity, number of prior term pregnancies, and male fetus.LB, live birth; SB, stillbirth.