Prenatal exposure of diurnal temperature range and preterm birth: Findings from a birth cohort study in China

Background: An increasing number of epidemiological studies have shown that daily hot and cold temperatures are associated with preterm birth (PTB). However, the relationship between daily temperature variation and PTB is poorly understood.

Objectives: This study aimed to investigate the role of prenatal exposure to diurnal temperature range (DTR), the difference between the daily maximum and minimum temperatures, in the risk of PTB.

Methods: A total of 11,056 women who gave birth to a live singleton infant were recruited from the Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Hospital), from September 2012 to October 2014. Daily temperature data were obtained from the official website of China Meteorological Administration. A binary logistic regression model was used to estimate the association between DTR and PTB.

Results: Among the 11,056 live singleton births, 618 (5.6%) infants were PTB. Prenatal exposure to large DTR during the second week before delivery was significantly associated with an increased risk of PTB. After adjusting for the daily mean temperature, daily mean humidity, socioeconomic, obstetrical and lifestyle factors, each 1 °C incremental increase in DTR was associated with a 5.4% (95% CIs: 1.006, 1.104; P = 0.026) increased risk of PTB. The association between large DTR exposure and PTB was stronger for pregnant women with a higher pre-pregnancy BMI, older maternal age, and with delivery in cold season.

Conclusions: This is the first study to reveal the association between DTR and PTB in China. Health professionals and pregnant women should be aware of the influence of unstable temperature conditions on the risk of PTB.