Maternal exposure to ozone and risk of gestational hypertension and eclampsia in the United States.

BACKGROUND

Exposure to ambient ozone during pregnancy may be linked with hypertensive disorders in pregnancy, but evidence is largely unknown. We aimed to estimate the association between maternal exposure to ozone and risk of gestational hypertension and eclampsia in the contiguous United States (US).

METHODS

We included 2,393,346 normotensive mothers aged from 18 to 50 years old who had a live singleton birth documented in the National Vital Statistics system in the US in 2002. We obtained information on gestational hypertension and eclampsia from birth certificates. We estimated daily ozone concentrations from a spatiotemporal ensemble model. We used distributed lag model and logistic regression to estimate the association between monthly ozone exposure and risk of gestational hypertension or eclampsia after adjusting for individual-level covariates and county poverty rate.

RESULTS

Of the 2,393,346 pregnant women, there were 79,174 women with gestational hypertension and 6034 with eclampsia. A 10 parts per billion (ppb) increase in ozone was associated with an increased risk of gestational hypertension over 1-3 months before conception (OR = 1.042, 95 % CI: 1.029, 1.056), 2-3 months after conception (OR = 1.058, 95 % CI: 1.040, 1.077), and 3-5 months after conception (OR = 1.031, 95 % CI: 1.018, 1.044). The corresponding OR for eclampsia was 1.115 (95 % CI: 1.074, 1.158), 1.048 (95 % CI: 1.020, 1.077), and 1.070 (95 % CI: 1.032, 1.110), respectively.

CONCLUSIONS

Exposure to ozone was associated with an increased risk of gestational hypertension or eclampsia, especially during 2 to 4 months after conception.