Humid-heat shifts conceptions and increases pregnancy termination risks in Nigeria

Climate change is increasing the occurrence of dangerous heat events globally with immediate health consequences, particularly in the Global South. In this paper, we spatially integrate Demographic and Healt 9 h surveys with a high-resolution, blended remotely sensed and station-derived dataset of humid-heat events spanning 1983-2016 to examine the effect of humid-heat exposure on fertility in Nigeria, one of the largest and most climate-vulnerable countries in the world. We use discrete-time models to examine the relationship between humid-heat exposure and conception probability and linear probability models to examine the relationship between humid-heat exposure and pregnancy termination (spontaneous and induced). We find that a 1 ^°C increase in the current maximum wet bulb globe temperature decreases conceptions (0.2 conceptions per 1,000 woman-months, 95% CI: 0.03 to 0.4), but exposure to hotter temperatures 1 to 2 mo prior increases conception probability. Exposure to hot-humid temperatures during pregnancy increases probability of pregnancy termination (1.73 terminations per 100 pregnancies, 95% CI: 0.7 to 2.7). The net effect is an increase in births, but the timing may be shifted. Subgroup analyses reveal that effects of humid-heat on conception were larger for women residing in rural areas or in northern districts, or who are Muslim or have lower educational attainment, while the association between humid-heat and pregnancy termination was larger for women in southern areas, older women, and Christian women. Differences in how humid-heat affects populations may exacerbate existing inequalities. Overall, our analysis contributes to a better understanding of how humid-heat exposure affects fertility and reproductive health among women in the Global South.