An estimated 349,681 pregnancy losses per year in South Asia were associated with exposure to PM2.5 concentrations that exceeded India’s air quality level (more than 40 μg/m3), accounting for 7% of annual pregnancy losses in the region from 2000 to 2016, according to the report.

Poor air quality is correlated with a large proportion of pregnancy losses in India, Pakistan, and Bangladesh, according to a modeling study reported in The Lancet Planetary Health Journal, which notes that such losses are more frequent in northern India and Pakistan.

Exposure to air pollution above the WHO air quality guideline could have led to 29 percent of pregnancy losses. Although the WHO guidelines aim at a safer level of air pollution, the authors note that India’s standard is a more achievable target level, given the high average levels of air pollution in the area and the need to balance practical governance and public health.

Considering the first research to estimate the impact of air pollution on pregnancy loss across the country, the limitations in the survey data suggest that it was not possible to differentiate between natural pregnancy loss and abortion, which may have contributed to an underestimation of the effect of air pollution on natural pregnancy loss.

The researchers included 34,197 women who had lost their pregnancy, including 27,480 miscarriages and 6,717 stillbirths, relative to live birth control. Of the cases of pregnancy loss, 77 percent were from India, 12 percent from Pakistan, and 11 percent from Bangladesh.

The authors incorporated data from household health surveys from 1998 to 2016 (from women who reported at least one pregnancy loss and one or more live births) and estimated PM2.5 exposure during pregnancy by satellite combination with atmospheric modeling outputs.

A model was built to analyze how exposure to PM2.5 increased women’s risk of pregnancy loss, and to quantify the risk for each 10 μg/m3 increased PM2.5 after adjusting for maternal age, temperature and humidity, seasonal variance, and long-term pregnancy loss patterns.

Using this connection, they estimated the number of pregnancy losses that could have been caused by PM2.5 in the entire region for the period 2000–16 and looked at how many pregnancy losses could have been avoided under the Indian and WHO air quality requirements (40 μg/m3 and 10 μg/m3, respectively).

Gestational exposure to PM2.5 was associated with an increased risk of pregnancy loss, which remained important after correction for other factors. Each increase of 10 μg/m3 was estimated to increase the maternal risk of pregnancy loss by 3%, according to the report.

Lead study author Tao Xue of Beijing University says: “South Asia has the highest burden of pregnancy loss worldwide and is one of the most contaminated PM2.5 regions in the world. Our findings indicate that poor air quality may be responsible for a substantial burden of pregnancy loss in the area, providing more evidence for urgent action to address hazardous levels of pollution.”