Adverse Weather Conditions can have Negative Effects on Birth Outcomes: Evidence from a birth registry cohort in Tanzania
Authors: Amiel Castro Rita T. , Marti Beatrice , Mmbaga Blandina T. , Siegfried Tobias , Bernauer Thomas , Ehlert Ulrike 
Published: January 2024

AbstractClimate change is bound to have particularly serious implications for public health in the least developed countries. Based on unique registry data from the Kilimanjaro Christian Medical Centre in Tanzania from 2001-2015, we aimed to investigate whether pregnancy exposure to weather conditions affects neonatal birthweight, length, head circumference, and Apgar scores and to evaluate changes in weather conditions across the studied period. Methods: N=30,068 pregnant women were assessed through a postpartum interview whereas baby data were obtained through medical records. Environmental data - rainfall, temperature, the multivariate ENSO index (MEI), the effective drought index, and harvest - were obtained through the Kilimanjaro International Airport weather station and examined during pregnancy and a preconception trimester. Our main analytical strategy was hierarchical regression analyses. Results: Analyses revealed a median birthweight of 3,185 g (IQR:600), a mean length of 49 cm (IQR:71) and a mean head circumference of 34 cm (IQR:24). Lower birthweight was associated with consecutive days with temperatures >30°C (B-.01, CI95% -.00 - .05) in the third gestational trimester, poor harvest (B-.13, CI95% -.10 -.08) and the interaction between insufficient rain and poor harvest (B.20, CI95% .13 -.26). Shorter length was significantly associated with more days with temperatures >30°C at preconception (B-.01, CI95% -.00 - .04) and in all gestational trimesters (range:B-.01 - -.02, CI95% - .00 - -.06). Smaller head circumference was associated with more consecutive days with temperatures >30°C at preconception (B-.01, CI95% -.00 - .03) and with MEI (B-.01, CI95% -.01 - .05) in the first trimester. Conclusions: Overall, exposure to adverse weather during pregnancy is associated with more negative birth outcomes. Therefore, climate change adaptation efforts should pay greater attention to limiting pregnant women’s exposure to adverse weather.Key messagesWhat is already known on this topicThe effect of adverse weather on the incidence of some pregnancy disorders has been well-documented, but less is known about the effects on health at birth of intrauterine exposure to adverse climate conditions.Health at birth is an important determinant of physical development, cognitive achievement, and work outcomes.Global warming has the potential to negatively affect millions with great impacts expected on public health.What this study addsThis study highlights that adverse weather conditions are associated with more negative birth outcomes, which may have lasting unfavorable health impact.In a large registry-based study, we found that more consecutive days with higher temperature, poor harvest and an interaction between insufficient rain and poor harvest contributed to lower birthweight.More days with elevated temperature was associated with shorter neonatal length, whereas more consecutive days with elevated temperature was linked to smaller head circumference.Apgar scores were hardly affected by adverse weather conditions.Particularly for Tanzania, our results suggest long-term climate-driven health and economic challenges.How this study might affect research, practice or policyThe study findings may help policy makers to prioritize and develop programs aiming to reduce climate stress whilst increasing medical preparedness and care for adverse birth outcomes.Mitigation of climate effects on pregnant women should receive greater attention than has hitherto been the case in climate change adaptation policy.The study points to the need to examine the precise biological mechanisms linking pregnancy and birth outcomes to different weather conditions.