Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Faculty of Nursing and Health Sciences, Nord University, Bodø, Norway.
Int J Gynaecol Obstet. 2024 Dec;167(3):1168-1177. doi: 10.1002/ijgo.15789. Epub 2024 Jul 16.
The aim of the present study was to examine and quantify whether the association between preterm birth (PTB) and pre-pregnancy body mass index (BMI) is mediated by gestational weight gain (GWG).
This is a secondary analysis of a large randomized community non-inferiority trial using a cohort design. The data of 26 101 pregnant women in their first trimester who sought prenatal care and met eligibility criteria were included. The four-way decomposition method was applied to screen for all types of association effects of pre-pregnancy BMI on the risk of PTB. These effects include the total, direct, and various indirect effects including pure mediation via GWG, interactive effects with GWG, and mediated interaction with GWG, all adjusted for potential confounders.
Among the study participants, 24 461 (93.7%) had term deliveries, while 1640 (6.3%) experienced PTB. The results of the study showed that there was a positive association between pre-pregnancy BMI among those with BMI more than 25 kg/m and the risk of PTB and this association was negatively mediated and interacted by GWG, which differed quantitatively between those who had inadequate, adequate, or excessive GWG. The total association effect showed that the risk was lowest for those who had underweight pre-pregnancy BMI and adequate GWG (excess relative risk [RR]: 0.06, 95% CI: 0.01-0.11, P value: 0.022) and was highest for those who had obese pre-pregnancy BMI and excessive GWG (excess RR: 0.67, 95% CI: 0.35-1.00, P value <0.001).
The findings of the present prospective population-based study demonstrated that pre-pregnancy BMI >25 kg/m is directly and positively associated with the risk of preterm birth. The highest risk of preterm birth was observed among individuals with an obese pre-pregnancy BMI who also experienced excessive GWG.
本研究旨在检验并量化早产（PTB）与孕前体重指数（BMI）之间的关联是否由妊娠体重增加（GWG）介导。
这是一项使用队列设计的大型随机社区非劣效性试验的二次分析。纳入了 26101 名在孕早期寻求产前保健并符合入选标准的孕妇的数据。应用四向分解法筛选孕前 BMI 对 PTB 风险的所有类型关联效应。这些效应包括总效应、直接效应以及包括通过 GWG 纯中介、与 GWG 相互作用以及与 GWG 中介相互作用在内的各种间接效应，均针对潜在混杂因素进行了调整。
在研究参与者中，24461 人（93.7%）分娩足月，而 1640 人（6.3%）发生早产。研究结果表明，BMI 超过 25kg/m 的孕妇孕前 BMI 与 PTB 风险呈正相关，这种关联被 GWG 负向介导和交互作用，而 GWG 在 GWG 不足、充足或过多的孕妇之间存在数量差异。总关联效应表明，对于那些孕前 BMI 不足且 GWG 充足的孕妇，风险最低（超额相对风险 [RR]：0.06，95%CI：0.01-0.11，P 值：0.022），而对于那些孕前 BMI 肥胖且 GWG 过多的孕妇，风险最高（RR：0.67，95%CI：0.35-1.00，P 值<0.001）。
本前瞻性基于人群的研究结果表明，孕前 BMI>25kg/m 与早产风险直接正相关。孕前 BMI 肥胖且 GWG 过多的个体发生早产的风险最高。
