Fine particulate matter from urban air pollution can cross the placental barrier and disrupt critical foetal development by triggering inflammation and suppressing a key growth-regulating protein, according to new research from the All India Institute of Medical Sciences (AIIMS), Delhi.
The ICMR-funded study, published in EMBO Molecular Medicine, provides the most comprehensive molecular pathway to date linking maternal exposure to particulate matter (PM2.5) with adverse pregnancy outcomes and potential long-term effects on children.
Researchers found that exposure to urban particulate matter activates inflammatory pathways in the placenta, which in turn inhibit the expression of IGFBP3 - a protein essential for maintaining placental balance and supporting embryonic growth. Reduced IGFBP3 levels impair nutrient exchange, blood vessel formation, and overall placental function, leading to restricted foetal growth.
"Our research reveals that exposure during pregnancy to Urban Particulate Matter activates inflammatory pathways that inhibit IGFBP3 expression, a key protein governing the equilibrium of the placenta and growth of the embryo. This reduction in IGFBP3 impairs critical placental processes, resulting in restricted foetal growth and altered developmental trajectories," said Subhradip Karmakar, Professor of Biochemistry at AIIMS Delhi and corresponding author of the paper.
The study combined human epidemiological data with detailed animal experiments. Researchers analysed delivery records of 994 women from high-pollution Delhi and low-pollution Deoghar in Jharkhand. In Delhi, PM2.5 exposure emerged as a significant risk factor for low birth weight, while higher pollution levels were also associated with increased rates of preeclampsia.
In parallel rodent studies simulating Delhi's pollution levels, pregnant rats exposed to the particulates showed clear placental damage. The pollution impaired the placenta's ability to invade the uterine wall, form the nutrient-exchange layer, and develop adequate blood vessels. It also induced severe oxidative stress and epigenetic changes that alter gene expression.
These effects translated into measurable outcomes: litter sizes reduced by up to 25 per cent, placentas were smaller, and newborns weighed about 34 per cent less at term compared to controls. Offspring also exhibited neurological deficits, including impaired motor coordination, heightened anxiety-like behaviour, and altered stress responses - signs consistent with prenatal origins of later developmental issues.
While earlier research had established that PM2.5 and PM10 can cross the placental barrier and cause oxidative stress and inflammation, the AIIMS study stands out for tracing the full biological cascade from exposure to molecular disruption and clinical consequences in a unified framework.
Dr. Karmakar noted that previous work had examined isolated aspects of this process. "We showed the entire pathway," he emphasised.
The researchers cautioned that the full scope of long-term impacts - including potential effects on motor development, cognitive function, cardiovascular health, cancer risk, and metabolic disorders in later life - requires further transgenerational studies.
They suggested immediate practical measures such as pregnant women using masks in highly polluted areas and consuming antioxidant-rich diets as interim protections. However, they stressed that systemic pollution control remains essential.
"Risk mitigation in terms of controlling pollution will have to be multi-dimensional," Dr. Karmakar said. "The research findings call for pollution monitoring to be integrated into prenatal care."
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