The adverse effects of air pollution on the lungs and heart are well known and often spoken about. Exposure to the toxic pollutants in the air can affect even the reproduction system. A study conducted by the National Institutes of Health NIH has suggested that exposure to common air pollutants such as ozone and fine particles may increase the risk of early pregnancy loss. The study published online November 16 2017 in the journal Fertility and Sterility examined the effect of the exposure to ozone in 501 couples based on pollution levels in their residential communities. Ozone is a highly reactive form of oxygen that is a primary constituent of urban smog. Ninety seven 28 of the 343 couples who achieved pregnancy experienced an early pregnancy loss before 18 weeks. Couples with higher exposure to ozone had a 12 greater risk of suffering an early pregnancy loss. Couples exposed to particulate matter were 13 more likely to experience a loss. Although the cause of pregnancy loss is not well understood impaired fetal development due to increased inflammation of the placenta and oxidative stress has been suggested as a possible factor. Based on the findings of the study pregnant women are advised to curtail outdoors activity when pollution levels are high and the air quality is of hazardous level. Source NIH November 16 2017