Women who live near motorways are more likely to give birth prematurely, research suggests.
The link between the concentration of major road routes around a woman's home and early birth is revealed in a study of 970 mothers and their newborn babies in Logan City, south of Brisbane.
"The most striking result was the reduction in gestation time of 4.4 per cent - or almost two weeks - associated with an increase in freeways within 400m of the women's home," said Associate Professor Adrian Barnett, from the Queensland University of Technology's Institute of Health and Biomedical Innovation.
Professor Barnett has previously published a study that found a strong association between increased air pollution and small fetus size.
"Although the increased risks are relatively small, the public health implications are large because everyone living in an urban area gets exposed to air pollution," he said.
"Pre-term and low-birth weight babies stay in hospital longer after birth, have an increased risk of death and are more likely to develop disabilities."
Professor Barnett said that while air pollution levels in southeast Queensland were low compared with industrial cities, people's exposure to chemical toxins in vehicle emissions was relatively high because of our outdoor lifestyle and open houses.
Similar living conditions can be found in Auckland.
The study counted the number of roads around the mothers' homes up to a 500m radius.
"We examined the distance between the home and busy roads to find the distance at which most of the negative effects on birth outcomes occurred, because this has implications for local governments planning expansions or new roads," Professor Barnett said.
The effects of noise pollution were considered to be a possible contributing factor. "Disturbed sleep during pregnancy may cause extra stress and be a risk factor for adverse birth outcomes."