Estimating the burden of temperature-related low birthweight attributable to anthropogenic climate change in low-income and middle-income countries: a retrospective, multicentre, epidemiological study.

Background: Pregnant individuals are particularly susceptible to non-optimal temperatures due to their physiological status. Moreover, pregnancy is a crucial period for programming fetal health. Quantifying the impact of non-optimal temperature exposure and the contribution of anthropogenic climate change is crucial for mitigating and adapting to climate-related health risks. However, this has not been thoroughly studied in pregnant individuals in low-income and middle-income countries (LMICs).

Methods: Using data from 511 449 births across 31 LMICs from 1990 to 2018, we linked climate simulations (with and without anthropogenic forcing) to spatiotemporally resolved temperature data and birthweight records. We assessed the association between heat and cold exposure (ie, >90th and <10th percentile of temperature by region) during pregnancy and birthweight across different regions. We then used temperature simulations from both historically forced and natural-only forced climate models to estimate changes in exposure due to anthropogenic climate change and to quantify the burden of temperature-related low birthweight (ie, a birthweight <2500 g) attributable to anthropogenic climate change.

Findings: Heat exposure during pregnancy, compared with the optimal temperature range, was associated with an increased risk of low birthweight in several regions: southern Asia (odds ratio 1·41, 95% CI 1·34-1·48), western Africa (1·12, 1·02-1·24), and eastern Africa (1·40, 1·27-1·55). Cold exposure increased the risk of low birthweight in central Africa (1·31, 1·10-1·56), southern Africa (1·18, 1·02-1·36), and eastern Africa (1·14, 1·02-1·26). Anthropogenic climate change contributed to approximately 59·2% (95% CI 16·6-94·3), 89·0% (51·0-100·0), and 77·3% (27·0-100·0) of heat-related low birthweight cases in southern Asia, western Africa, and eastern Africa, respectively. Conversely, in regions where cold exposure was predominant, anthropogenic climate change reduced the burden of low birthweight.

Interpretation: Our study provides quantitative estimates of the contribution of anthropogenic climate change to the low birthweight burden in LMICs. These findings can inform strategies for climate mitigation and adaptation in LMICs and help reduce global health inequalities.

Funding: National Natural Science Foundation of China.