Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA.
J Matern Fetal Neonatal Med. 2024 Dec;37(1):2321486. doi: 10.1080/14767058.2024.2321486. Epub 2024 Mar 3.
The US still has a high burden of preterm birth (PTB), with important disparities by race/ethnicity and poverty status. There is a large body of literature looking at the impact of pre-pregnancy obesity on PTB, but fewer studies have explored the association between underweight status on PTB, especially with a lens toward health disparities. Furthermore, little is known about how weight, specifically pre-pregnancy underweight status, and socio-economic-demographic factors such as race/ethnicity and insurance status, interact with each other to contribute to risks of PTB.
The objective of this study was to measure the association between pre-pregnancy underweight and PTB and small for gestational age (SGA) among a large sample of births in the US. Our secondary objective was to see if underweight status and two markers of health disparities - race/ethnicity and insurance status (public vs. other) - on PTB.
We used data from all births in California from 2011 to 2017, which resulted in 3,070,241 singleton births with linked hospital discharge records. We ran regression models to estimate the relative risk of PTB by underweight status, by race/ethnicity, and by poverty (Medi-cal status). We then looked at the interaction between underweight status and race/ethnicity and underweight and poverty on PTB.
Black and Asian women were more likely to be underweight (aRR = 1.0, 95% CI: 1.01, 1.1 and aRR = 1.4, 95% CI: 1.4, 1.5, respectively), and Latina women were less likely to be underweight (aRR = 0.7, 95% CI: 0.7, 0.7). Being underweight was associated with increased odds of PTB (aRR = 1.3, 95% CI 1.3-1.3) and, after controlling for underweight, all nonwhite race/ethnic groups had increased odds of PTB compared to white women. In interaction models, the combined effect of being both underweight and Black, Indigenous and People of Color (BIPOC) statistically significantly reduced the relative risk of PTB (aRR = 0.9, 95% CI: 0.8, 0.9) and SGA (aRR = 1.0, 95% CI: 0.9, 1.0). The combined effect of being both underweight and on public insurance increased the relative risk of PTB (aRR = 1.1, 95% CI: 1.1, 1.2) but there was no additional effect of being both underweight and on public insurance on SGA (aRR = 1.0, 95% CI: 1.0, 1.0).
We confirm and build upon previous findings that being underweight preconception is associated with increased risk of PTB and SGA - a fact often overlooked in the focus on overweight and adverse birth outcomes. Additionally, our findings suggest that the effect of being underweight on PTB and SGA differs by race/ethnicity and by insurance status, emphasizing that other factors related to inequities in access to health care and poverty are contributing to disparities in PTB.
美国仍然面临着较高的早产（PTB）负担，其在不同种族/族裔和贫困状况下存在显著差异。大量文献研究了孕前肥胖对 PTB 的影响，但很少有研究探讨体重过轻对 PTB 的关联，特别是从健康差异的角度来看。此外，人们对体重，特别是孕前体重过轻，以及社会经济人口统计学因素（如种族/族裔和保险状况）如何相互作用以增加 PTB 风险知之甚少。
本研究旨在衡量美国大量出生人群中孕前体重过轻与 PTB 和小于胎龄儿（SGA）之间的关联。我们的次要目的是观察体重过轻状况以及两个健康差异指标——种族/族裔和保险状况（公共保险与其他保险）——与 PTB 的关系。
我们使用了 2011 年至 2017 年加利福尼亚州所有分娩的数据，这些数据包括 3070241 例单胎分娩和相关的医院出院记录。我们使用回归模型来估计体重过轻状况、种族/族裔和贫困（医疗补助状况）与 PTB 的相对风险。然后，我们观察了体重过轻状况与种族/族裔以及体重过轻与贫困对 PTB 的交互作用。
黑人女性和亚裔女性更有可能体重过轻（相对风险[aRR]分别为 1.0、95%置信区间[CI]：1.01、1.1 和 aRR = 1.4、95% CI：1.4、1.5），而拉丁裔女性体重过轻的可能性较小（aRR = 0.7、95% CI：0.7、0.7）。体重过轻与 PTB 的几率增加相关（aRR = 1.3、95% CI 1.3-1.3），并且在控制体重过轻后，与白人女性相比，所有非白人种族/族裔群体的 PTB 几率均增加。在交互模型中，体重过轻且为黑人和原住民以及有色人种（BIPOC）的综合效应在统计学上显著降低了 PTB 的相对风险（aRR = 0.9、95% CI：0.8、0.9）和 SGA（aRR = 1.0、95% CI：0.9、1.0）。体重过轻且参加公共保险的综合效应增加了 PTB 的相对风险（aRR = 1.1、95% CI：1.1、1.2），但体重过轻且参加公共保险对 SGA 没有额外的影响（aRR = 1.0、95% CI：1.0、1.0）。
我们证实并扩展了之前的发现，即孕前体重过轻与 PTB 和 SGA 风险增加有关——这一事实往往在关注超重和不良出生结局时被忽视。此外，我们的研究结果表明，体重过轻对 PTB 和 SGA 的影响因种族/族裔和保险状况而异，这强调了与获得医疗保健和贫困相关的其他不平等因素正在导致 PTB 差异。
