AIR pollution limits the growth of babies in the final months before birth, according to a “landmark” study from a Scottish university.

Reduced birth weight has been linked to exposure to cigarettes in the womb, as well as many other factors.

Now scientists from Aberdeen University say they have found a link with gases found in air pollution – and discovered when this affects unborn children.

The team, led by Professor Steve Turner, reviewed a decade’s worth of research evidence from around the world as they worked to determine the extent to which the exposure of mothers to alcohol consumption, chemicals, diet and air pollution impacts on fetal growth.

While they found “insufficient evidence” that poor diet, drinking or chemicals were factors, the experts uncovered proof that exposure to nitrogen dioxide – emitted from motor vehicle exhausts, manufacturing and the burning of gas and coal – resulted in smaller head size in unborn babies.

The effect was particularly pronounced in the last three months of pregnancy.

Although not considered a greenhouse gas, nitrogen dioxide is a noted pollutant that contributes to smog.

Other sources include cigarette smoke and both butane and kerosene heaters and stoves.

Revealing the results, Turner said the project has done something no others have.

He stated: “In our research we looked at all the studies that measured the effects of mothers’ exposures to everyday substances including air pollutants, alcohol, and diet on the size of the unborn baby, measured through ultrasound from half way through the pregnancy onwards.

“What was unique about our review of the literature is that we looked at unborn babies to see if mothers’ exposures to these factors affected fetal development.

“We used medical literature dating back 13 years, when the first studies linking exposure to fetal measurements was first published.

“The seven studies where air pollution was measured and linked to fetal size were from different geographical areas of the world, including Australia, the USA and several countries in Europe. However in all of the studies the evidence was clear that in the third trimester in particular, exposure to nitrogen dioxide reduced fetal growth.”

Turner continued: “Previous research has shown that being small, for gestational age, at birth is associated with increased risk for conditions that include coronary artery disease, type II diabetes and asthma.

“Our research has shown that the link between exposure and fetal growth is apparent well before birth, so any potential interventions need to happen in the early stages of pregnancy.

“Furthermore, the findings also suggest that public health measures are urgently required to minimise pregnant mothers’ exposures to nitrogen dioxide.”