Mothers living in urban areas with a high level of greenery are more likely than those in less green areas to deliver at full term and have babies of higher birth weight, according to a new study published in the journal Environmental Health Perspectives.
The findings held even when factors such as socioeconomic status, walkability, and exposure to air pollution and noise were controlled for, according to the researchers from Oregon State University in the US, the University of British Columbia in Canada and Utrecht University in The Netherlands.
“This was a surprise,” Dr Perry Hystad, an environmental epidemiologist in the College of Public Health and Human Sciences at Oregon State and lead author of the study, said.
“We expected the association between greenness and birth outcomes to disappear once we accounted for other environmental exposures such as air pollution and noise. The research really suggests that greenness affects birth outcomes in other ways, such as psychologically or socially.”
The researchers said they were not sure what caused the relationship between greenness and birth outcomes, though psychological effects – such as greenery reducing stress and depression – or social effects – such as greenery providing more opportunity for socialising, increasing sense of belonging – could be contributors. More research, they said, would be necessary to tease out these hypotheses.
In the study, which looked at more than 64,000 births in Vancouver, Canada, researchers found that very pre-term births were 20 per cent lower and moderate pre-term births 13 per cent lower for infants whose mothers lived in greener suburbs. Fewer infants in greener suburbs were considered small for their gestational age, with babies from the greener suburbs weighing 45 grams more at birth, Dr Hystad said.
The results could have significant implications for public health, Dr Hystad said, as underweight and premature babies often had more health and developmental problems through life.
“From a medical standpoint, those are small changes in birthweight, but across a large population, those are substantial differences that would have a significant impact on the health of infants in a community,” he said.
Senior author Professor Michael Brauer from the University of British Columbia said the results could inform better planning and urban development.
“We know a lot about the negative influences such as living closer to major roads, but demonstrating that a design choice can have benefits is really uplifting,” Professor Brauer said.
“With the high cost of healthcare, modifying urban design features such as increasing green space may turn out to be extremely cost-effective strategies to prevent disease, while at the same time also providing ecological benefits.
There was, however, a “threshold of greenness” needed for the benefits of green space to be realised. A next step is to find out what the threshold is and why it makes a difference.
“We know green space is good. How do we maximise that benefit to improve health outcomes?” Dr Hystad said. “The answer could have significant implications for land use planning and development.”