Department of Environmental and Occupational Health, The George Washington University, Washington, District of Columbia, USA.
Resilience Creative, New York, NY, USA.
Environ Health. 2024 Sep 27;23(1):78. doi: 10.1186/s12940-024-01116-9.
Exposure to ambient air pollution is a top risk factor contributing to the global burden of disease. Pregnant persons and their developing fetuses are particularly susceptible to adverse health outcomes associated with air pollution exposures. During pregnancy, the thyroid plays a critical role in fetal development, producing thyroid hormones that are associated with brain development. Our objective is to systematically review recent literature that investigates how prenatal exposure to air pollution affects maternal and fetal thyroid function.
Following the Navigation Guide Framework, we systematically reviewed peer-reviewed journal articles that examined prenatal exposures to air pollution and outcomes related to maternal and fetal thyroid function, evaluated the risk of bias for individual studies, and synthesized the overall quality and strength of the evidence.
We found 19 studies that collected data on pregnancy exposure windows spanning preconception to full term from 1999 to 2020 across nine countries. Exposure to fine particulate matter (PM) was most frequently and significantly positively associated with fetal/neonatal thyroid hormone concentrations, and inversely associated with maternal thyroid hormone concentrations. To a lesser extent, traffic-related air pollutants, such as nitrogen dioxide (NO) had significant effects on fetal/neonatal thyroid function but no significant effects on maternal thyroid function. However, the body of literature is challenged by risk of bias in exposure assessment methods and in the evaluation of confounding variables, and there is an inconsistency amongst effect estimates. Thus, using the definitions provided by the objective Navigation Guide Framework, we have concluded that there is limited, low quality evidence pertaining to the effects of prenatal air pollution exposure on maternal and fetal thyroid function.
To improve the quality of the body of evidence, future research should seek to enhance exposure assessment methods by integrating personal monitoring and high-quality exposure data (e.g., using spatiotemporally resolved satellite observations and statistical modeling) and outcome assessment methods by measuring a range of thyroid hormones throughout the course of pregnancy.
暴露于环境空气污染是导致全球疾病负担的首要风险因素。孕妇及其发育中的胎儿特别容易受到与空气污染暴露相关的不良健康后果的影响。在怀孕期间，甲状腺在胎儿发育中起着至关重要的作用，产生与大脑发育相关的甲状腺激素。我们的目的是系统地回顾最近的文献，调查产前暴露于空气污染如何影响母婴甲状腺功能。
根据导航指南框架，我们系统地回顾了同行评议的期刊文章，这些文章研究了产前暴露于空气污染与母婴甲状腺功能相关的结果，评估了个别研究的偏倚风险，并综合了证据的总体质量和强度。
我们发现了 19 项研究，这些研究从 1999 年到 2020 年在九个国家收集了跨越受孕前至足月的妊娠暴露窗的数据。细颗粒物 (PM) 的暴露与胎儿/新生儿甲状腺激素浓度呈最频繁和显著的正相关，与母体甲状腺激素浓度呈负相关。在较小程度上，交通相关的空气污染物，如二氧化氮 (NO)，对胎儿/新生儿的甲状腺功能有显著影响，但对母体甲状腺功能没有显著影响。然而，文献的主体受到暴露评估方法和混杂变量评估的偏倚风险的挑战，并且效应估计值不一致。因此，根据客观导航指南框架提供的定义，我们得出结论，关于产前空气污染暴露对母婴甲状腺功能的影响，仅有有限的低质量证据。
为了提高证据的质量，未来的研究应寻求通过整合个人监测和高质量暴露数据（例如，使用时空分辨率卫星观测和统计建模）来改进暴露评估方法，并通过在整个妊娠过程中测量一系列甲状腺激素来改进结果评估方法。
