Ambient Air Pollution Exposure Associated With Increased Risk for Pregnancy Loss

Chronic exposure to particulate matter with a diameter ≤2.5 μm (PM_2.5) and ozone throughout pregnancy was associated with an increased risk for pregnancy loss, according to the results of a recent prospective cohort study published in Fertility and Sterility.

A total of 343 singleton pregnancies with detailed protocols for ovulation and pregnancy testing were eligible for analysis in the study. The main outcome measure was the timing of incident pregnancy loss from ovulation. The incidence of pregnancy loss reported in the study was 28% (97 of 343 pregnancies).

Levels of pollutants at the pregnant women’s residences were estimated using modified Community Multiscale Air Quality models and were averaged during the previous 2 weeks (defining acute exposure) and during the entire pregnancy (defining chronic exposure).

Based on Cox proportional hazards modeling, an interquartile range increase in average whole pregnancy ozone (hazard ratio [HR], 1.12; 95% CI, 1.07-1.15) and PM_2.5 (HR, 1.13; 95% CI, 1.03-1.24) concentrations were both associated with a faster time to pregnancy loss. In addition, sulfate compounds seemed to increase a woman’s risk for pregnancy loss (HR, 1.58; 95% CI, 1.07-2.34). Exposure to ambient air pollutants in the last 2 weeks of pregnancy was not associated with a higher risk for pregnancy loss.

The investigators concluded that in a prospective cohort of couples trying to conceive and residing in geographic areas with low to moderate background levels of air pollution, exposure to air pollution throughout the pregnancy was linked with loss.

Larger preconception studies with daily measured air quality are warranted to delineate more precisely the specific periods of heightened vulnerability in pregnant women residing in certain geographic locales.

Reference

Ha S, Sundaram R, Buck Louis GM, et al. Ambient air pollution and the risk of pregnancy loss: a prospective cohort study [published online November 14, 2017]. Fertil Steril. doi: 10.1016/j.fertnstert.2017.09.037