Smoking during pregnancy in relation to grandchild birth weight and BMI trajectories

Background
Maternal smoking has been linked to lower birth weight and higher risk of childhood obesity. However, it is unknown whether grand-maternal smoking during pregnancy is associated with grandchildren birth weight and body mass index (BMI) trajectories.
Methods
We investigated associations of smoking during pregnancy with birth weight, risks of overweight and BMI trajectories among 46,858 mother-child dyads and 6,583 grandmother-mother-child triads of three cohort studies of related individuals. Smoking during pregnancy was reported by mothers, and anthropometric data were provided by participants in each cohort.
Results
Compared to grandchildren of non-smoking women, grandchildren of women who smoked more than 14 cigarettes per day throughout pregnancy were 70 g (95% CI: 12, 129 g; P for trend = 0.01) heavier at birth, and 18% (95% CI: 4%, 34%; P for trend = 0.01) more likely to become overweight. The mean BMI of grandchildren of women who smoked during pregnancy was 0.45 kg/m2 (95% CI: 0.14, 0.75 kg/m2; P for trend = 0.006) higher through adolescence and young adulthood than that of grandchildren of non-smoking mothers.
Conclusions
Grandmothers’ smoking during pregnancy was associated with higher birth weight, higher risk of overweight, and higher BMI through adolescence and young adulthood.

【背景】母亲孕期吸烟与子代出生体重降低及儿童肥胖风险升高相关，但目前尚不清楚外祖母孕期吸烟是否与孙辈的出生体重及体质量指数（Body Mass Index，BMI）轨迹存在关联。
【方法】本研究针对三项基于亲缘个体的队列研究展开分析，纳入46858对母婴二元队列及6583组外祖母-母亲-孙辈三元队列，探讨孕期吸烟与孙辈出生体重、超重风险及BMI轨迹的关联。其中，孕期吸烟情况由母亲报告，各队列参与者提供人体测量学数据。
【结果】与不吸烟女性的孙辈相比，整个孕期每日吸烟超过14支的女性的孙辈出生体重高出70g（95%置信区间：12~129g；趋势检验P=0.01），发生超重的风险升高18%（95%置信区间：4%~34%；趋势检验P=0.01）。在青春期及青年成年期，孕期吸烟女性的孙辈平均BMI较不吸烟母亲的孙辈高0.45 kg/m²（95%置信区间：0.14~0.75 kg/m²；趋势检验P=0.006）。
【结论】外祖母孕期吸烟与孙辈出生体重升高、超重风险增加及青春期至青年成年期体质量指数升高显著相关。