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Background:
Preterm birth is a major determinant of adverse health consequences. Often, the specific cause of preterm birth is unclear. However, there are known genetic, behavioral, socioeconomic and environmental risk factors. Considering climate change, temperature is an important factor to consider. Several studies have focused on associations of ambient air temperature (Ta) with risk of preterm birth. Climates studied and methods used varied and results have been inconsistent. Few studies included early-term births.
Aims:
To investigate the association of prenatal exposure to Ta with preterm and early-term birth in a semi-arid climate in Israel.
Methods:
All singleton deliveries at the Soroka Medical Center, Be’er Sheva, Israel, with estimated conception dates between May 2004 and March 2013 (N=62,547) were linked to prenatal Ta estimates from a spatiotemporally resolved model, with daily 1 km resolution. We used time-dependent Cox regression models with weekly mean Ta throughout gestation, adjusted for calendar month and year of conception, ethnicity, SES and population density. Effect modification by fetal sex and ethnicity was examined using interaction terms and stratified.
Results:
Ta was positively associated with late preterm birth (31+0/7 - 36+6/7 weeks of gestation), with increased risk in the upper Ta quintile as compared to the middle Ta quintile, hazard ratio (HR) = 1.31, 95% CI = 1.11 - 1.56. Ta was also associated with early term birth (37+0/6 - 38+6/7 of gestation), with increased risk in the upper Ta quintile as compared to the middle Ta quintile, HR = 1.24, 95% CI = 1.13 - 1.36. Ta was more strongly associated with late preterm birth for female fetuses than for male fetuses (HR = 1.50, 95% CI = 1.17-1.94 and HR = 1.17, 95% CI = 0.97-1.41, respectively).
Conclusion:
Prenatal exposure to high Ta is associated with a higher risk of early delivery in southern Israel.