Extreme temperature increases the risk of stillbirth in the third trimester of pregnancy

Abstract

Epidemiological studies have reported the association between extreme temperatures and adverse reproductive effects. However, the susceptible period of exposure during pregnancy remains unclear. This study aimed to assess the impact of extreme temperature on the stillbirth rate. We performed a time-series analysis to explore the associations between temperature and stillbirth with a distributed lag nonlinear model. A total of 22,769 stillbirths in Taiwan between 2009 and 2018 were enrolled. The mean stillbirth rate was 11.3 ± 1.4 per 1000 births. The relative risk of stillbirth due to exposure to extreme heat temperature (> 29 °C) was 1.18 (95% CI 1.11, 1.25). Pregnant women in the third trimester were most susceptible to the effects of extreme cold and heat temperatures. At lag of 0–3 months, the cumulative relative risk (CRR) of stillbirth for exposure to extreme heat temperature (29.8 °C, 97.5th percentile of temperature) relative to the optimal temperature (21 °C) was 2.49 (95% CI: 1.24, 5.03), and the CRR of stillbirth for exposure to extreme low temperature (16.5 °C, 1st percentile) was 1.29 (95% CI: 0.93, 1.80). The stillbirth rate in Taiwan is on the rise. Our findings inform public health interventions to manage the health impacts of climate change.

Maternal preconceptional and prenatal exposure to El Niño Southern Oscillation levels and child mortality: a multi-country study

“…As deaths are usually considered rare events, HR and relative risk (RR) were assumed to be a reasonable approximation of each other in this study with caution 53 – 55 . Then, regression coefficients corresponding to ENSO measures were used to calculate the AF of deaths and the number of deaths attributable to extreme levels of ENSO, using commonly described approaches as follows 56 : where RR is approximated by the HR of La Niña, weak El Niño, or moderate El Niño conditions considering the neutral condition as the reference. We calculated the number of deaths attributable to exposure to La Niña, weak El Niño, or moderate El Niño by multiplying the AF with the number of deaths under these conditions.…”

Heat exposure and perinatal mortality: A time-stratified, case-crossover study from 16 hospitals in Benin, Malawi, Tanzania and Uganda

“…6,28 Comparing our effects of ambient temperature on stillbirth mortality with other estimates is challenging as studies are heterogeneous in terms of exposure metric, unit change, and time period of effect. Generally, evidence is stronger for an acute effect of heat (i.e., in the last weeks or trimester of pregnancy) [29][30][31][32][33][34] than for a delayed effect occurring in the 1st or 2nd trimester. 16,34 Few studies have evaluated associations between temperature in the week before birth and stillbirths as we did.…”

“…Generally, evidence is stronger for an acute effect of heat (i.e., in the last weeks or trimester of pregnancy) [29][30][31][32][33][34] than for a delayed effect occurring in the 1st or 2nd trimester. 16,34 Few studies have evaluated associations between temperature in the week before birth and stillbirths as we did. A recent systematic review and meta-analysis (Chersich et al, 6 ) included two studies from high income countries using the same analysis method (lag 0-6).…”

An expert review of environmental heat exposure and stillbirth in the face of climate change: Clinical implications and priority issues

“…In Western Australia, risk of stillbirth was found to increase by 19% (95% CI 17%–21%) when women were exposed to moderate heat stress (99th centile UTCI, 31.7°C) versus no thermal stress (50th centile UTCI, 13.9°C) throughout the last week of pregnancy, and by 41% (95% CI 38%–44%) when exposed to moderate heat stress throughout the last 2 weeks of pregnancy 25 . In Taiwan, Yang et al 26 estimated that 2.64% of all stillbirths are attributable to high ambient temperature exposures (>29°C). They found that women are most susceptible to adverse heat effects in the third trimester of pregnancy, with a 2.4‐fold (95% CI 1.19–4.8) increased risk of stillbirth when exposed to the 99th centile of monthly mean temperature (30.1°C) versus the optimal temperature (21°C) 0–3 months before delivery.…”