ABSTRACT
Evidence is accumulating, both in the US and abroad, of the apparent serious health impacts of various environmental exposures tied to climate change. High ambient temperature, or heat, is a worsening global health risk. Heat risk is affected by many factors such as the magnitude, duration, and timing of exposure - such as specific, critical windows during pregnancy. This article focuses on the association of heat with both adverse pregnancy and newborn health outcomes. Regarding pregnancy, studies link heat and preterm birth, low birth weight and stillbirth. Multiple potential mechanisms support the biological plausibility of these associations. Emerging evidence suggests that heat, via epigenetics, may affect maternal health far beyond pregnancy. For newborn health impacts, heat is associated with increased hospitalization, neurologic and gastrointestinal dysfunction, and infant death. Research gaps include the need to study neonates separately from children and determining the mechanisms linking heat to adverse outcomes. We also highlight disparate adverse reproductive health outcomes for communities of color and low income tied to disproportionate exposures to environmental stressors like heat. Finally, we summarize educational and clinical tool resources for clinicians, information for patients, and opportunities for near-term action using the precautionary principle framework.
Subject(s)
Hot Temperature , Premature Birth , Pregnancy , Child , Female , Infant, Newborn , Humans , Infant Health , Stillbirth , Infant, Low Birth WeightABSTRACT
Importance: Knowledge of whether serious adverse pregnancy outcomes are associated with increasingly widespread effects of climate change in the US would be crucial for the obstetrical medical community and for women and families across the country. Objective: To investigate prenatal exposure to fine particulate matter (PM2.5), ozone, and heat, and the association of these factors with preterm birth, low birth weight, and stillbirth. Evidence Review: This systematic review involved a comprehensive search for primary literature in Cochrane Library, Cochrane Collaboration Registry of Controlled Trials, PubMed, ClinicalTrials.gov website, and MEDLINE. Qualifying primary research studies included human participants in US populations that were published in English between January 1, 2007, and April 30, 2019. Included articles analyzed the associations between air pollutants or heat and obstetrical outcomes. Comparative observational cohort studies and cross-sectional studies with comparators were included, without minimum sample size. Additional articles found through reference review were also considered. Articles analyzing other obstetrical outcomes, non-US populations, and reviews were excluded. Two reviewers independently determined study eligibility. The Arskey and O'Malley scoping review framework was used. Data extraction was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline. Findings: Of the 1851 articles identified, 68 met the inclusion criteria. Overall, 32â¯798â¯152 births were analyzed, with a mean (SD) of 565â¯485 (783â¯278) births per study. A total of 57 studies (48 of 58 [84%] on air pollutants; 9 of 10 [90%] on heat) showed a significant association of air pollutant and heat exposure with birth outcomes. Positive associations were found across all US geographic regions. Exposure to PM2.5 or ozone was associated with increased risk of preterm birth in 19 of 24 studies (79%) and low birth weight in 25 of 29 studies (86%). The subpopulations at highest risk were persons with asthma and minority groups, especially black mothers. Accurate comparisons of risk were limited by differences in study design, exposure measurement, population demographics, and seasonality. Conclusions and Relevance: This review suggests that increasingly common environmental exposures exacerbated by climate change are significantly associated with serious adverse pregnancy outcomes across the US.
