Poor air quality is associated with a considerable proportion of pregnancy loss in India, Pakistan, and Bangladesh, according to a modelling study to be published on Thursday in The Lancet Planetary Health journal.
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 standard (more than 40 µg/m³), accounting for 7% of annual pregnancy loss in the region from 2000-2016
Previous studies have suggested a link between air pollution and pregnancy loss in other regions, but this is the first study to quantify the burden in South Asia, which is the most populous region in the world and has the highest rate of pregnancy loss, Lead author on the study, Dr. Tao Xue, Peking University, China, told The Indian Express via email. Therefore, understanding the risk factors for pregnancy loss in South Asia is crucial to improving maternal health regionally and globally, he said.
“Among some of the explanations why air pollution can cause pregnancy loss is that fine particles have been reported to cross the blood placenta barrier and harm the embryo directly. Exposure to poor air quality can cause disorders such as inflammation, oxidative stress and blood pressure elevation which can act as factors to increase the risk of pregnancy loss,” Dr Tao said.
To carry out their analysis, the authors combined data from household surveys on health from 1998-2016 (from women who reported at least one pregnancy loss and one or more live births) and estimated exposure to PM2.5 during pregnancy through combining satellite with atmospheric modelling outputs. They created a model to examine how exposure to PM2.5 increased women’s risk of pregnancy loss, calculating risk for each 10 µg/m³ increased in PM2.5 after adjusting for maternal age, temperature and humidity, seasonal variation, and long-term trends in pregnancy loss.
Using this association, they calculated the number of pregnancy losses that may have been caused by PM2.5 in the whole region for the period 2000–16 and looked at how many pregnancy losses might have been prevented under India’s and WHO’s air quality standard (40 µg/m³ and 10 µg/m³, respectively).
In the study, they included 34,197 women who had lost a pregnancy, including 27,480 miscarriages and 6,717 stillbirths, which were compared to live birth controls. Of the pregnancy loss cases, 77% were from India, 12% from Pakistan, and 11% from Bangladesh.
Gestational exposure to PM2.5 was associated with an increased likelihood of pregnancy loss, and this remained significant after adjusting for other factors. Each increase in 10 µg/m³ was estimated to increase a mother’s risk of pregnancy loss by 3%. The increase in risk was greater for mothers from rural areas or those who became pregnant at an older age, compared to younger mothers from urban areas.
Although WHO’s guidelines aims for a safer level of air pollution, the authors said that India’s standard is a more realistic target level, given the high average levels of air pollution in the region and the need to balance practical governance and public health.
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