Birth weight percentiles among stillbirths and live births.

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 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 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.

基于SCRN算法（SCRN algorithm）[17]计算的死胎（死亡时）或活产（分娩时）的胎龄（gestational age, GA）相关出生体重数据。由于四舍五入误差，百分比总和可能略高于或略低于100%。
a. 仅纳入百分位分组效应的logistic回归模型中，给定百分位组新生儿与参照组新生儿相比的死胎未校正比值比（odds ratio, OR）。
b. 除百分位分组变量外，还纳入了研究中心编号、父亲年龄（见表1或另有说明）以及母亲年龄的logistic回归模型中，给定百分位组新生儿与参照组新生儿相比的死胎校正比值比（OR）。
c. 分析权重考虑了基础研究设计及抽样的其他相关因素。未加权样本量为527例死胎与1821例活产。用于校正比值比计算的未加权（加权）样本量分别为452（451）例死胎与1665（1261）例活产。
d. 个体化百分位常模基于Bukowski等人[15]提出的胎龄胎儿体重计算公式推导得到。
e. 超声相关百分位常模基于Hadlock等人[19]提出的胎龄胎儿体重计算公式及标准误推导得到。
f. 采用Alexander等人[18]提出的人群出生体重胎龄百分位常模。针对以整周数报告的Alexander出生体重胎龄百分位数据，通过简单线性插值法推导得到以周和天表示的胎龄对应的出生体重百分位。
LB：活产（live birth）；SB：死胎（stillbirth）。