Centre for Analysis of Social Exclusion, London School of Economics, London, UK.
Centre of Methods and Policy Application in the Social Sciences (COMPASS), Faculty of Arts, University of Auckland, Auckland, New Zealand.
J Epidemiol Community Health. 2018 Dec;72(12):1124-1131. doi: 10.1136/jech-2017-209074. Epub 2018 Sep 10.
International evidence indicates relationships between pre-pregnancy body mass index (BMI) and breastfeeding behaviours. This study aims to assess associations between key points in the breastfeeding trajectory (initiation, early cessation and longevity) and pre-pregnancy BMI in a recent, nationally representative British cohort. It also aims to explore in the British context potential moderation by mothers' ethnic group.
The sample comprises 17 113 mothers from the UK Millennium Cohort Study who have information on pre-pregnancy BMI. Associations between pre-pregnancy BMI categories and breastfeeding initiation, early cessation and longevity are tested using logistic regression. Directed acyclic graphics identify appropriate minimal adjustment to block biasing pathways and classify total and direct effects.
After adjusting for confounders, there are large differences in breastfeeding early cessation and longevity by pre-pregnancy BMI group. Differences in propensity to initiation are negligible. Having begun breastfeeding, overweight and obese mothers are more likely to cease in the first week and less likely to continue past 4 months. Observed potential mediators within pregnancy and delivery provide little explanation for relationships. Evidence for moderation by ethnicity is scant.
The causal mechanisms underlying relationships between pre-pregnancy overweight, obesity, and breastfeeding behaviours require further research. However, this study suggests pre-pregnancy BMI as one predictive measure for targeting support to women less likely to establish breastfeeding in the early days, and to continue beyond 4 months. The nature of support should carefully be considered and developed, with mind to both intended and potential unintended consequences of intervention given the need for additional investigation into the causes of associations.
国际证据表明，孕前体重指数（BMI）与母乳喂养行为之间存在关联。本研究旨在评估英国最近一项全国代表性队列中母乳喂养轨迹（起始、早期中断和持续时间）的关键指标与孕前 BMI 之间的关联，并探讨在英国背景下，母亲的种族群体是否存在潜在的调节作用。
该样本包括来自英国千禧年队列研究的 17113 名母亲，她们有孕前 BMI 的信息。使用逻辑回归测试孕前 BMI 类别与母乳喂养起始、早期中断和持续时间之间的关联。有向无环图确定适当的最小调整以阻断偏差路径，并对总效应和直接效应进行分类。
在调整了混杂因素后，孕前 BMI 组之间的母乳喂养早期中断和持续时间存在很大差异。起始倾向的差异可以忽略不计。已经开始母乳喂养的超重和肥胖母亲更有可能在第一周中断，不太可能持续到 4 个月以上。妊娠和分娩期间观察到的潜在中介因素几乎不能解释这些关系。关于种族群体调节作用的证据很少。
孕前超重、肥胖与母乳喂养行为之间关系的因果机制需要进一步研究。然而，本研究表明，孕前 BMI 是一种预测指标，可以针对那些不太可能在早期建立母乳喂养的女性提供支持，并支持她们持续母乳喂养 4 个月以上。支持的性质应仔细考虑和制定，考虑到干预的预期和潜在意外后果，因为需要进一步调查这些关联的原因。
