aAbout 140 million children Born in the world last year-Equivalent Adding a whole new Russia to the world’s population. Do not count among those usually blessed events the number of families whose pregnancies end tragically. According to the United Nations Interagency Group for Child Mortality EstimationAround 2 million pregnancies worldwide end in stillbirth each year. There are many causes of death at birth – from fetal abnormalities, to labor complications, to high blood pressure in the mother, to infections, to placental abnormalities.
Now, according to a new study in Nature CommunicationsAnother particularly insidious cause may be responsible for up to 39.7% of stillbirths in low- and middle-income countries: air pollution, specifically in the form of fine particles measuring 2.5 microns—or millionths of a meter—or less. The particles, about 3% the width of a human hair, typically come from vehicle exhaust, the burning of coal and heating oil, and natural sources such as wildfires.
According to the new research, led by ecologist and public health specialist Tao Xue at the Peking University Health Science Center in Beijing, every 10 micrograms — or millionths of a gram — of so-called PM2.5 particles per cubic meter of air increases the risk of stillbirth by 11. %, with greater losses to older mothers than to younger children.
“The United Nations describes the global burden of stillbirth as a neglected tragedy,” the paper’s authors write. “Preventing stillbirth depends on a comprehensive understanding of the underlying risk factors.”
The World Health Organization (WHO) has established what is called a reference level – or maximum safe exposure – of PM2.5 at 5 micrograms per cubic meter of air. Above this level, the particles can contribute to heart disease, asthma, decreased lung function, and premature death in people with pre-existing heart or lung disease. Researchers have long linked a possible relationship between PM2.5 exposure and stillbirth, but what they didn’t do, until Tao and his colleagues took up the topic, was study how the burden falls disproportionately on people in poor countries.
According to the World Bank, the global average concentration of PM2.5 is an alarming 46 micrograms per cubic meter – or nine times the WHO reference level. But the burden is not distributed evenly. In Australia, 9 mcg is more likely; In Canada, the number is just six. The Bahamas clocks in at just 5.58. Nowhere else, in the less developed world, is the problem of pollution more impactful.
To conduct their study, the investigators selected 137 low- and middle-income countries where the data were from Department of Health Surveys (DHS), a division of the United States Agency for International Development (USAID), has been found to be home to 98% of the world’s stillbirths. They compared these death figures to other data from the World Health Organization Air quality guidelines It details the severity of PM2.5 pollution in each of those countries. The results drew a bright line between particulate matter emissions and the incidence of stillbirths.
India, the hardest hit country, with an annual average of 217,000 deaths (out of 25 million live births), had a PM2.5 concentration of 60.15 micrograms per cubic meter of air – or 12 times the WHO reference level. Pakistan, the second most affected country, with 110,000 deaths per year (compared to 6.075 million live births), weighed in at 63.16 micrograms of pollution. followed by Nigeria (93,000 deaths, 7.8 million live births, 69.66 μg); China (64,000 stillbirths, 10.6 million live births, 51.11 μg) and Bangladesh (49,000 stillbirths, 2.8 million live births, 69.58 μg). In addition to PM2.5 air pollution, the study also points to the possibility of naturally occurring high concentrations of dust – particularly in sub-Saharan Africa and the Arabian Sahara region – as another source of hazardous particulate matter.
Maternal age played a significant role in mortality risk. Drawing on data from the Demographic and Health Surveys, as well as two existing meta-analyses of the incidence of stillbirth, the researchers estimated that mothers who lost their children at birth were, on average, 3.81 years older than those whose children were successfully delivered. The greatest risk of stillbirth in countries with a high incidence of PM2.5 was among mothers 34 years of age or older.
What mechanism links PM2.5 concentration to stillbirths is uncertain. “Although the potential biological mechanisms of the association between exposure to PM2.5 particulate matter and pregnancy loss are not yet clear, some pathways could explain this to some extent,” the researchers wrote. The researchers suggested three possibilities.
First, when a pregnant woman inhales PM2.5 particles, they enter the bloodstream and may directly cross the placental barrier where they flow into the fetus, leading to low oxygen levels or immune problems in the baby, both of which can be linked to fetal death. There is also the possibility that exposure to PM2.5 could lead to the development of methemoglobin in the parent – a form of hemoglobin that does not bind oxygen and therefore does not provide adequate amounts of oxygen to the fetus, which also leads to immune problems and possibly death in utero. Finally, PM2.5 can lead to abnormalities or abnormalities in the placenta itself, preventing it from sustaining the fetus throughout pregnancy.
The outlook was not entirely bleak. The study notes that the global stillbirth rate actually decreased by 1.95% from 2000 to 2009, and fell again by 2.05% from 2009 to 2019. The study attributes the trend to improved air quality in several countries – particularly China, which is taking slow steps. of coal-fired power plants and cleaning up their power grid with renewables.
Meanwhile, pregnant women can take steps to reduce their exposure to PM2.5 pollution and better monitor the potential impact of particulate matter. Wearing N95 or KN95 masks outdoors on highly polluted days, avoiding the outdoors when air quality is at its worst, and installing air purifiers at home can help. So do improvements in prenatal care and timely intervention – including caesarean sections – in premature or complicated labour.
Pregnancy and childbirth have never been so easy. But more often than they do now, they must produce a happy outcome. In at least 137 countries, our poor stewardship of the health of the planet often deprives families of this happiness.
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