Exposure to ambient air pollution from the preconceptional period and risk of gestational hypertension

Although accumulative studies have revealed the associations between air pollutants and elevated risk of gestational hypertension (GH), evidence from developing countries with relatively higher levels of air pollutants remains limited. In this retrospective study, a total of 45,439 birth records were collected in Beijing, China from 2013 to 2018. For PM2.5, SO2, NO2, and O3, exposure windows from the 3rd month of preconception to the 6th month of conception and the averages of 3 months of preconception, trimester 1 and trimester 2 periods were all calculated for assessment of GH risks. The correlations between air pollutants and the risk of GH were analyzed by logistic regression model. Our results showed that exposure to PM2.5 and SO2 in the preconceptional and early pregnancy periods was related to the elevated risk of GH. Furthermore, 3 months preconceptional exposure to PM2.5 (PCPM2.5: OR = 1.134 (1.114, 1.155)) and SO2 (PCSO2: OR = 1.158 (1.135, 1.181)) showed a higher risk of GH than the results of the trimester 1 (T1PM2.5: OR = 1.131 (1.104, 1.159); T1SO2: OR = 1.164 (1.141, 1.187)) and the trimester 2 (T2PM2.5: OR = 1.154 (1.126, 1.182); T2SO2: OR = 1.121 (1.098, 1.144)). The study also found significant and higher OR values for PCPM2.5, and PCSO2 from 2013 to 2016 when air pollution was serious in Beijing compared with 2017 to 2018 when the air pollution was obviously improved. Subgroup analysis also found that during 3 months of preconception women with higher age and who exposure to higher temperatures showed higher GH risk from PM2.5 and SO2 than that of the younger group and who exposure to lower temperature, respectively. Collectively, our findings suggest that air pollution exposure was adversely associated with GH in pregnant women and the preconceptional period is a critical air pollution exposure window for GH. Improving air quality can benefit public health, especially for sensitive populations like pregnant women.