During pregnancy, air enters the house without asking permission. It passes through windows, gets on your clothes, comes from busy streets, from running engines, from dust that no one sees and which ends up everywhere. We often talk about smog when the city turns grey, when the eyes burn, when breathing gets heavier. Here, however, the question comes much earlier. Before the pram, before the first steps, before the first word said badly and repeated a thousand times in the living room. It descends into pregnancy.
A new study from King’s College London has linked maternal exposure to air pollution in pregnancy to slower signs in children’s development at 18 months. The work analyzed 498 newborns from the Greater London area, recruited at St Thomas’ Hospital between 2015 and 2020, evaluating language, cognitive abilities and motor skills with standardized clinical tests. In children exposed to higher levels of pollutants during the first trimester, language scores were on average 5-7 points lower than those of children exposed to lower levels.
The pollutants considered are those that we now also know in our cities: atmospheric particulates and nitrogen dioxide, substances largely linked to traffic, exhaust, combustion, to that daily mixture that makes certain apparently normal streets a biologically more aggressive environment. In the group of children born prematurely, the association was even more delicate: higher exposure during gestation was also linked to lower motor scores, with an average difference of 11 points compared to children exposed to lower levels.
The months that weigh
The first trimester, from conception to the twelfth-thirteenth week, represents a very fine construction phase. The fetal brain begins to organize itself, circuits, connections and trajectories are prepared which in the following months and years will become language, movement, attention, the ability to be in the world. The study speaks of association, therefore of increased risk observed in the data, without transforming each exposure into a written condemnation. This distinction matters. The research indicates a vulnerability, an extra pressure, a probability that shifts.
The data, however, remains inconvenient. Also because the levels observed in London children were within the annual limits set by British legislation in 2010, despite exceeding the more conservative thresholds indicated by the World Health Organization in 2021. In other words, the air can be legal and continue to weigh on the development of the little ones. A fairly dry thing, to keep on the table without beating around the bush.
To make the picture bigger there is a huge number: according to the WHO, 99% of the world’s population breathes air that exceeds the organization’s guidelines and contains high levels of pollutants, with heavier exposures in low- and middle-income countries. Air pollution during pregnancy, therefore, concerns London, Milan, Rome, Delhi, Dhaka, the suburbs crossed by arterial roads, the neighborhoods where greenery arrives later, if it arrives, and where clean air almost becomes a real estate privilege.
Inequality breathes first
The hardest part is risk distribution. Mothers breathe different air depending on where they live, how much they can choose their home, how much they can avoid a congested street, how much the neighborhood was designed to protect those who live there. The poorest and most marginalized communities more often remain close to major traffic routes, industrial areas, urban spaces where noise and fine dust are part of the decor. The problem begins environmentally and immediately becomes social.
Even in Italy, pediatricians have long insisted on the first thousand days, the period from conception to two years of life. The Italian Society of Pediatrics reminds us that this window has a particular weight because what happens in that period can also have long-term effects on health. SIP itself reports studies linking prenatal PM2.5 exposure to low birth weight, prematurity and, in some research, poorer outcomes on cognitive and motor tests.
Translated into daily life, it means that child protection begins before the nursery, before the Montessori games, before choosing a kindergarten. It starts from the air of the streets, from home-to-work routes, from the neighborhoods crossed by cars, from urban policies that always seem far from the belly of a pregnant woman and instead end up inside, molecule after molecule.
Clean air, public health
The work of King’s College adds a piece to an already underway discussion: the air breathed during pregnancy can be a modifiable factor. Modifiable on an individual level only up to a certain point, because a mother can avoid, when possible, the busiest roads, choose green areas, control the worst times, protect the child within the limits of reality. The SIP recommends, among other things, reducing passage in congested areas, also remembering the vulnerability of children in strollers, closer to exhaust fumes.
The rest concerns the cities. It concerns public transport that works, real limits on traffic, schools far from the most polluted routes, accessible green areas, transparent monitoring, rules built on the health of children and pregnant women, rather than on the statistical tolerability of pollution. Fine particles have this unpleasant characteristic: they enter public discourse as numbers, micrograms per cubic meter, annual averages, thresholds, tables. Then they arrive in the body as concrete exposure.
The London study also leaves an important caution. The researchers report that further follow-ups will be needed to understand whether the children will recover over time or whether those differences measured at 18 months may have consequences later, during school and in the learning processes. It is a necessary prudence, because serious science proceeds like this: it measures, corrects, observes, waits. Meanwhile the signal remains on.
Air pollution during pregnancy calls for a much less romantic form of protection than the one we put in baby advertisements. Fewer bows, fewer pastel-colored bedrooms, more control units, sidewalks, buses, limits, real trees, breathable streets. The health of a child can also begin there, at any intersection, with a traffic light holding back a row of engines running.
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