A major new scientific review has confirmed that exposure to air pollution during pregnancy significantly increases the risk of babies being born prematurely or with low birth weight, effects that can last a lifetime.
Only last week we reported how exposure to common air pollutants during the earliest weeks of pregnancy can increase the risk of depression throughout pregnancy and this week we bring expectant mothers more disturbing news.
The research, published in the Journal of Environmental Health Science and Engineering, synthesises evidence from dozens of epidemiological studies and mechanistic investigations to paint a detailed picture of how polluted air reaches and harms the developing foetus.
The research found that a 10 μg/m³ increase in PM2.5 exposure during the second trimester is associated with an 11.8 gram reduction in birth weight and a 23.1% increase in the risk of preterm birth. More than 45% of deaths among children under five occur within the first 28 days of life, with preterm birth standing as the primary cause of neonatal mortality.
The review, led by researchers from University Medical Center Mainz in Germany, identifies several biological pathways through which air pollution damages fetal development, with the placenta being particularly vulnerable.
Oxidative stress emerges as a key mechanism. When pregnant women breathe polluted air, fine particles can cross the lung barrier and enter the bloodstream, triggering inflammation and the production of damaging free radicals throughout the body. The placenta, with its high metabolic demands, is especially susceptible to this assault.
Inflammation follows closely behind. Studies show that exposure to PM2.5, PM10, nitrogen dioxide, and ozone during pregnancy is linked to elevated levels of inflammatory markers such as C-reactive protein and interleukin-6 in both maternal and umbilical cord blood. These same markers are independently associated with preterm birth and restricted foetal growth.
The researchers also highlight evidence that air pollution can disrupt hormone function, alter placental blood flow and cause epigenetic changes – modifications to DNA that affect how genes are expressed without changing the underlying genetic code. These changes may have effects that extend well beyond birth.
The researchers stress that the burden falls disproportionately on vulnerable populations, and that the effects may be modified by factors such as maternal nutrition, physical activity, and pre-pregnancy body mass index – though evidence on these protective factors remains limited.
They call for stricter air quality regulations, cleaner energy transitions, and targeted protection for pregnant women, stressing that every 10 μg/m³ increase matters.
The full research can be read here
Photo: lucas mendes
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