Is birth weight associated with pregestational maternal BMI? BRISA Cohort, Ribeirão Preto, Brazil

Given the increase of women with excess weight or obesity and its possible effects on birth weight, the present study aimed to investigate the association between pregestational maternal body mass index (BMI) and birth weight in a birth cohort from Ribeirão Preto, SP, Brazil. This was a prospective study conducted on 1362 mother-child pairs involving singleton births. The women were evaluated using standardized questionnaires during the second trimester of pregnancy and at the time of childbirth. Information about the newborns was obtained from their medical records. The dependent variable was birth weight, categorized as low, adequate, or high. The independent variable was pregestational maternal BMI, categorized as malnutrition, adequate weight, overweight, and obesity. A multinomial regression model was used to estimate the crude and adjusted relative risk (RR) of low and high birth weight. A high frequency of pregestational excess weight (39.6%) was detected and found to be independently associated with high birth weight (RR=2.13, 95%CI: 1.19-3.80 for overweight and RR=3.34, 95%CI: 1.80-6.19 for obese pregnant women). There was no association between pregestational malnutrition and low birth weight (RR=1.70; 95%CI: 0.81-3.55). The present data showed a high rate of women with excess pregestational weight, supporting the hypothesis that pregestational BMI may contribute to high birth weight babies and indicating the need for actions aiming to prevent excessive weight in women at reproductive age.

鉴于超重或肥胖女性群体规模持续扩大，且该状况可能对新生儿出生体重产生潜在影响，本研究旨在探究巴西圣保罗州里贝朗普雷图市某出生队列中，孕前母亲体重指数（Body Mass Index, BMI）与新生儿出生体重之间的关联。本研究为前瞻性研究，共纳入1362对单胎活产的母婴对子。研究对象在妊娠中期及分娩时通过标准化问卷完成评估，新生儿相关信息均取自其分娩病历档案。本研究的因变量为新生儿出生体重，分为低出生体重、适宜出生体重与高出生体重三类；自变量为孕前母亲BMI，分为营养不良、体重正常、超重及肥胖四类。本研究采用多项式回归模型，估算低、高出生体重的粗相对风险与校正后相对风险（Relative Risk, RR）。结果显示，孕前超重或肥胖的女性占比达39.6%，且该状况与新生儿高出生体重存在独立相关性：超重孕妇的相对风险RR=2.13，95%置信区间（Confidence Interval, CI）为1.19~3.80；肥胖孕妇的相对风险RR=3.34，95%CI为1.80~6.19。而孕前营养不良与低出生体重未发现显著关联（RR=1.70，95%CI：0.81~3.55）。本研究数据表明孕前超重女性占比偏高，这一结果支持孕前BMI可能是新生儿高出生体重的影响因素这一假说，并提示需采取干预措施以预防育龄女性体重过度增长。