New Delhi: A study conducted by researchers in AIIMS, Delhi has traced the exact biological chain through which urban air pollution damages unborn babies, shutting down a protein critical for foetal growth and causing effects that can stretch into late childhood.The ICMR-funded work, published in EMBO Molecular Medicine, lays out for the first time the step-by-step molecular process by which particulate matter PM2.5 and PM10 can breach the placental barrier and trigger oxidative stress and inflammation that disrupt foetal development, The Hindu reported.The fallout includes placental dysfunction, preterm birth, low birth weight and preeclampsia.“Since we know that pollutants do affect foetuses, our primary goal,” Subhradip Karmakar, professor of biochemistry at AIIMS, Delhi and corresponding author of the paper was quoted as saying by TH, “was to examine the pathways that enable the pollutants to cause distress to the placenta and the foetus. While this has been studied before, it has been done in a piecemeal way. We showed the entire pathway.”The team found that exposure to urban particulate matter during pregnancy activates inflammatory pathways that suppress IGFBP3, a protein that helps balance placental function and embryo 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,” Karmakar added.To test this, the study looked at 994 deliveries across two cities: high-pollution Delhi and low-pollution Deoghar in Jharkhand. Next, the researchers ran parallel experiments on rodents.Among Delhi women, PM2.5 exposure emerged as a clear risk factor for low birth weight.Moreover, rates of preeclampsia, a dangerous rise in blood pressure during pregnancy, climbed as pollution levels went up. In rodents, the study found that particulate matter weakened the placenta’s ability to anchor into the uterine wall, form its nutrient-exchange layer, and grow blood vessels, TH reported.It also pushed cells into severe stress and flipped their epigenetic switches, permanently changing which genes turn on or off.The study found that pregnant rats exposed to Delhi’s pollution levels had litters that were up to 25% smaller, placentas that were reduced in size, and newborns that weighed 34% less at full term. The offspring also showed neurological deficits: poor motor coordination, higher anxiety, and altered stress responses which began in the womb, the paper noted.