The impact of ambient temperature on adverse pregnancy outcomes in Ahvaz, Iran; 2008-2018

Abstract

The impact of ambient temperature on adverse pregnancy outcomes in Ahvaz, Iran; 2008-2018AbstractBackground: There are few epidemiological studies on the relation between temperature changes and adverse pregnancy outcomes. The purpose of this study was to determine the relation between Diurnal Temperature Range (DTR), Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) with adverse pregnancy outcomes including stillbirth, low birth weight (LBW), preterm labor (PTL), spontaneous abortion (SA), preeclampsia and gestational hypertension in Ahvaz, Iran. Methods: Distributed Lag Non-linear Models (DLNM) combined with quasi-Poisson regression were used to investigate the effect of DTR, PET and UTCI on adverse pregnancy outcomes. In this study the effect of time trend, air pollutants (NO2, SO2 and PM10), and weekdays were adjusted. Results: Cold thermal stress in the DTR index (the 1st percentile (2.7 C°) compared to 25th percentile (11.9 C°) significantly increased the risk of abortion in the cumulative lags of 0-6, 0-13 and 0-21. High PET (45.4 C°, lag = 0) caused a significant increase in risk of stillbirth. Also, high levels of PET (45.4, 43.6, 42.5 C°, lag = 0-6) and low levels of PET (9.9, 16.9 C°, lags=0, 0-13, 0-21) significantly increased the risk of LBW. But, low levels of PET (6.4, 9.9, 16.9 C°, lags = 0-6, 0-13) reduced the risk of gestational hypertension. Low values of UTCI index (11.6 C°, lags = 0-6, 0-13) caused significant increase in risk of preterm labor. Finally, hot thermal stress in the UTCI index significantly increased the risk of stillbirth in 0-13 lag. Conclusions: The results of this study showed that hot and cold thermal stress are associated with increased risk of stillbirth, LBW, PTL and SA; in Ahvaz.