Forget pink or blue. It turns out that the best color for baby may be green.

In a study recently published in Environmental Health Perspectives, researchers found that mothers living in neighborhoods with plenty of greenness — grass, trees and other types of lush vegetation — were more likely to carry their pregnancies to full term and deliver babies at healthier weights. Specifically, the study found that very pre-term births were 20 percent lower and moderate pre-term births were 13 percent lower among mothers living in greener neighborhoods. Also, babies from greener neighborhoods were less likely to be classified as “small” for their gestational age than babies in less green neighborhoods. And the association between greenness and better birth outcomes stood up even after researchers adjusted for factors such as income, noise, neighborhood walkability and poor air quality.

“This was a surprise,” said study lead author Perry Hystad, an environmental epidemiologist in Oregon State University’s College of Public Health and Human Services, in a news release. “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.”

To conduct the study, researchers used satellite-derived data on vegetation and compared it with birth outcomes among 64,705 births in Vancouver, British Columbia. They noted in the study that with half of the world’s population living in urban areas — and with that number expected to grow — it’s important to understand the characteristics of urban environments that contribute to positive health outcomes. They found that birthweight was 20.6 grams higher on average with each 0.1 increase in greenness, with babies in the greenest neighborhoods weighing 45 grams more at birth than infants with moms living in the least green neighborhoods. In the news release, Hystad noted that even though the birthweight differences seem small on an individual basis, “those are substantial differences that would have a significant impact on the health of infants in a community.”

Why is this important? According to the Centers for Disease Control and Prevention, low birthweight is the “single most important factor” in newborn mortality and those babies who do survive can experience serious, long-term health problems. Overall, the study concluded that living within 100 meters of increased greenness was linked to healthier birthweights and a lower likelihood of preterm birth. Study authors Hystad, Hugh Davies, Lawrence Frank, Josh Van Loon, Ulrike Gehring, Lillian Tamburic and Michael Brauer write:

The fact that residential greenness exposure remained associated with birth outcomes after adjusting for a number of hypothesized environmental exposures suggests that alternative pathways may link greenness exposure to birth outcomes. Two well-hypothesized pathways that were not examined in this study include psychosocial and psychological influences. Greenness may facilitate positive psychosocial influences by providing shared spaces for interactions. For example, exposure to greenness has been associated with social support and increased social ties and community belonging. …While we were unable to examine these pathways, our findings of a persistent greenness association with birth outcomes that was independent of previously observed associations with noise and air pollution suggests more research is required that includes all potential pathways potentially linking greenness to birth outcomes.

The study authors noted that it’s unclear just how much green space and what type of greenery is of greatest benefit to newborns, but they did say that one or two potted plants won’t make a difference. And that’s the next step for researchers — examining exactly why greenness seems to make a difference and determining how much greenness it takes to impact newborn health. The answer could lead to one of the more low-cost and enjoyable ways to promote child health — planting more trees.

“We know that green space is good,” Hystad said. “How do we maximize that benefit to improve health outcomes? The answer could have significant implications for land use planning and development.”

To download a full copy of the study, visit Environmental Health Perspectives. And check out this article we published last month on the life-saving nature of trees.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for more than a decade.