Air pollution is a growing global concern, with significant implications for public health.
There is growing scientific evidence attributing adverse pregnancy outcomes to exposure to air pollution is increasingly recognized as a major threat to maternal and infant health. Expectant mothers exposed to polluted environments - whether from outdoor air pollution or indoor toxins such as cigarette smoke - face a higher risk of complications, including preterm birth, low birth weight, stillbirth, and congenital abnormalities.
External environmental factors, such as air pollution, play a critical role in disrupting the delicate processes of embryonic growth and differentiation.
A study titled "The role of smoke from cooking indoors over an open flame and parental smoking on the risk of cleft lip and palate: A case-control study in 7 low-resource countries" discussed at the Pan African Surgical Conference shed light on the risks associated with indoor air pollution. According to the research, children whose mothers were exposed to wood stove smoke during pregnancy were 49% more likely to be born with a cleft lip or palate.
Study participants included children from Vietnam, Philippines, Honduras, Nicaragua, Morocco, Congo, and Madagascar with cleft lip and palate and healthy newborns.
In developed countries exposure to smoke from cooking over open flames is rare. However, in low-resource regions, where about 80% of rural households rely on biomass fuels for cooking, indoor air pollution remains pervasive. Many low-resource settings also lack access to corrective surgery, making cleft lip and palate the most common birth defect.
South Africa is no exception.
Research conducted by the South African Medical Research Council (SAMRC) in collaboration with surgeons, researchers, and Operation Smile revealed that pregnant women living in air pollution hotspots are at a higher risk of giving birth to children with orofacial clefts.
"Yes, exposure to air pollution during pregnancy has been linked to an increased risk of birth defects, including cleft lip and cleft palate," said Dr. Caradee Wright, Chief Specialist Scientist at the SAMRC's Environment and Health Research Unit, and the lead researcher of the study.
She said that emerging evidence indicates that specific air pollutants - such as particulate matter (PM₂.₅), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), and polycyclic aromatic hydrocarbons (PAHs) - can disrupt foetal development, particularly during the early stages of pregnancy when the baby's facial structures are forming.
"Several studies have found associations between maternal exposure to high levels of air pollution and an increased likelihood of cleft lip or palate," said Dr. Wright. "For example, exposure to PM₂.₅ and PAHs, which are commonly emitted from vehicle exhaust, industrial processes, and biomass burning, has been linked to developmental abnormalities in animal and human studies. These pollutants can cause oxidative stress, inflammation, and DNA damage, potentially disrupting normal tissue fusion in the developing face."
Dr. Wright said that the risks of air pollution to maternal and fetal health vary significantly between high-income and low-income countries, largely due to differences in pollution sources, healthcare access, and mitigation strategies. In low-income countries, women are frequently exposed to high levels of household air pollution from burning biomass fuels like wood, charcoal, and dung for cooking and heating. This exposure has been linked to adverse outcomes such as low birth weight, preterm birth, stillbirth, and birth defects. In addition, outdoor air pollution from traffic, industry, and dust contributes to respiratory illnesses and pregnancy complications.
She said that limited healthcare access in these regions further exacerbates the health risks, as pregnant women may not receive timely prenatal care or interventions.
"In contrast, high-income countries benefit from stricter air quality regulations, better healthcare infrastructure, and greater access to cleaner energy sources," said Dr. Wright. "However, urban air pollution - primarily from traffic emissions, industrial activities, and wildfires - remains a concern."
Dr. Wright said that studies in high-income countries have shown that exposure to pollutants such as fine particulate matter (PM₂.₅) and nitrogen dioxide (NO₂) can increase the risk of preterm birth, low birth weight, and developmental issues. Even at lower pollution levels compared to low-income countries, prolonged exposure to air pollution can have subtle but significant effects on maternal and fetal health.
"Different regions have taken various approaches to address air pollution risks during pregnancy," she said.
She said that high-income countries have successfully reduced pollution-related pregnancy complications through clean air policies and public awareness campaigns.
"High-income countries have implemented stringent emissions controls, air quality monitoring systems, and public health campaigns to raise awareness about pollution-related risks," said Dr. Wright. " For example, European cities have introduced low-emission zones, and the United States has strengthened clean air policies, leading to measurable reductions in pregnancy complications linked to air pollution."
She said that in low-income countries, initiatives such as providing cleaner cooking stoves, promoting renewable energy, and expanding maternal healthcare services have helped reduce exposure to harmful pollutants.
According to Dr. Wright, lessons from both settings suggest that comprehensive policies combining pollution reduction with healthcare improvements are essential.
"Low-income regions can benefit from investments in clean energy, air quality monitoring, and accessible maternal healthcare. Meanwhile, high-income regions must continue refining their pollution control strategies, especially in urban areas," she said. "Cross-regional collaboration, such as sharing research on pollution-related pregnancy risks and implementing proven interventions, can help mitigate these risks globally."
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Dr. Wright said that policymakers and public health officials need to find better ways to implement air quality legislation, standards, and monitoring. This includes resources and capacity so that air quality can be tracked and enforcing minimum emission licenses is also critical for polluting industries.
She said that many pregnant women remain unaware of the risks air pollution poses to fetal development. Public health campaigns often focus on smoking, nutrition, and prenatal care but do not emphasize air pollution as a risk factor. In low-income and rural areas, where pollution exposure may be highest, access to reliable health information is often limited.
She said that many households may lack the means to switch to cleaner energy sources, leaving them vulnerable to the harmful effects of indoor air pollution.
"We need to better understand the associations between exposure and birth outcomes as well as understanding when the critical window of exposure is during pregnancy that leads to this outcome. This could help refine guidelines for pregnant women and policymakers," said Dr. Wright.
