Ambient PM2.5 exposures and systemic inflammation in women with early pregnancy

The association between ambient fine particulate matter (PM2.5) and systemic inflammation in women with early pregnancy is unclear. This study estimated the effects of PM2.5 exposures on inflammatory biomarkers in women with normal early pregnancy (NEP) or clinically recognized early pregnancy loss (CREPL). Serum interleukin-1beta (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were measured in 228 early pregnant women recruited in Tianjin, China. Maternal PM2.5 exposures at lag 0 through lag 30 before blood collection were estimated using temporally-adjusted land use regression models. Daily exposures to ambient PM10, NO2, SO2, CO and 8-hours maximum ozone were estimated using city-level concentrations. Single-day lag effects at lag 0 through lag 7 were estimated using multivariable linear regression models. Distributed lag effects and cumulative effects over the preceding seven days and 30 days were estimated using distributed lag non-linear models. Serum IL-1β (8.0% increase at lag 3), IL-6 (33.9% increase at lag 5) and TNF-α (12.7% increase at lag 5) in early pregnant women were significantly increased with an interquartile range increase in PM2.5 exposures adjusted for temporal confounders and demographic characteristics. These effects were robust in several two-pollutant models. Distributed lag effects over the preceding 30 days also showed that the three cytokines were significantly increased with PM2.5 on some lag days. Among all cumulative effects of PM2.5 on the three cytokines in all subjects or in the two groups, only IL-6 was significantly increased in CREPL women over the preceding seven days and 30 days. No significant cumulative effect of PM2.5 was observed in NEP women. In conclusion, exposure to ambient PM2.5 may induce systemic inflammation in women in the first trimester of pregnancy. Whether the PM2.5-related cumulative increase in maternal IL-6 is involved in the pathogenic mechanisms of early pregnancy loss needs to be identified in future research.