Objective: To estimate the association of pregnancy loss with common air pollutant exposure. Ambient air pollution exposure has been
linked to adverse pregnancy outcomes, but few studies have investigated its relationship with pregnancy loss.
Design: Prospective cohort study.
Setting: Not applicable.
Patient(s): A total of 343 singleton pregnancies in a multisite prospective cohort study with detailed protocols for ovulation and
pregnancy testing.
Intervention(s): None.
Main Outcome Measure(s): Timing of incident pregnancy loss (from ovulation).
Result(s): The incidence of pregnancy loss was 28% (n ¼ 98). Pollutant levels at women's residences were estimated using modified
Community Multiscale Air Quality models and averaged during the past 2 weeks (acute) and the whole pregnancy (chronic). Adjusted
Cox proportional hazards models showed that an interquartile range increase in average whole pregnancy ozone (hazard ratio [HR] 1.12,
95% confidence interval [CI] 1.07–1.17) and particulate matter <2.5 mm (HR 1.13, 95% CI 1.03–1.24) concentrations were associated
with faster time to pregnancy loss. Sulfate compounds also appeared to increase risk (HR 1.58, 95% CI 1.07–2.34). Last 2 weeks of
exposures were not associated with loss.
Conclusion(s): In a prospective cohort of couples trying to conceive, we found evidence that exposure to air pollution throughout
pregnancy was associated with loss, but delineating specific periods of heightened vulnerability await larger preconception cohort
studies with daily measured air quality. (Fertil Steril 2018;109:148–53. 2017 by American Society for Reproductive Medicine.)