Pregnant women living in greener neighborhoods may experience lower levels of chronic stress, according to a Bar-Ilan University-led study that measured stress hormones accumulated over several months.
The researchers found that greater exposure to vegetation around the home during the second trimester of pregnancy was associated with lower concentrations of cortisol and cortisone, two hormones involved in the body’s response to stress.
The findings do not establish that greenery directly causes lower stress levels, but they add to growing evidence that access to natural surroundings may benefit maternal well-being.
“Our findings suggest that exposure to greenery around the home is associated with reduced chronic stress hormones during pregnancy,” said Sohini Bhattacharya, a doctoral candidate at Bar-Ilan University’s Azrieli Faculty of Medicine.
“This is important because prolonged exposure to elevated stress hormones can negatively affect both the mother and the developing fetus,” she said.
The study, published in the peer-reviewed journal Environmental Epidemiology, found that women living in greener environments during their second trimester had significantly lower concentrations of cortisol and cortisone in their hair.
The findings were consistent across several measures of residential greenery and across different distances surrounding participants’ homes, according to the study, which examined 385 pregnant women at the Helen Schneider Hospital for Women at Rabin Medical Center in Petach Tikvah.
Measuring stress over months
Unlike hormone measurements taken from blood, saliva or urine, which generally reflect stress over relatively short periods, hormone concentrations in hair can provide a record covering several months.
The researchers analyzed hair samples collected during the women’s second trimester, allowing them to assess longer-term exposure to cortisol and cortisone.
Both hormones play important roles in metabolism, immune function, sleep cycles and the maintenance of pregnancy. Persistently elevated levels, however, have been associated with adverse health effects for both mother and fetus.
Earlier research on greenery and stress has often relied on participants’ own assessments of their stress or on biological measurements reflecting only a brief period.
Few studies have used hair samples to examine chronic stress, and fewer still have focused on pregnant women, according to the researchers.
Greenery from above and at street level
The research team assessed the amount of vegetation surrounding participants’ homes in two ways.
First, it used satellite imagery and the Normalized Difference Vegetation Index, a widely used tool for measuring vegetation density.
The researchers also analyzed Google Street View images to examine greenery from a pedestrian’s perspective and distinguish among grass, trees and other forms of vegetation.
The findings were consistent across the two methods and across different distances surrounding the women’s homes, according to the study.
Women living in greener areas generally had lower concentrations of cortisol and cortisone in their hair.
Grass shows strongest association
One of the more unexpected findings was the apparent significance of grass.
Women living in neighborhoods with a greater proportion of visible grass around their homes had notably lower levels of both stress hormones than those living in areas with less grass.
The researchers said the finding could have practical implications for urban planners and policymakers, since grass and other vegetation may offer relatively inexpensive ways to improve the residential environment.
The study expanded on earlier research by the same team that found an association between residential greenery and lower hair-cortisol levels during the first trimester of pregnancy.
The new research examined an additional hormone, focused on the second trimester and used more detailed methods to assess the types of greenery around participants’ homes.
Urban planning and public health
The study’s lead researcher, Professor Keren Agay-Shay of the Azrieli Faculty of Medicine, said the findings support efforts to maintain and increase vegetation in residential neighborhoods.
“Our findings support efforts to preserve and expand green spaces and greenness in residential neighborhoods,” she said.
“As cities continue to grow around the world, integrating trees, grass and other vegetation into urban environments may provide a simple and accessible strategy for improving public health.”
The findings come as many populations are confronting heightened stress linked to war, climate change and rapid urbanization. Pregnant women may be particularly vulnerable to the effects of prolonged stress.
The research team is continuing to investigate how environmental conditions, including air pollution and temperature, may affect hormone levels during pregnancy.
The study was conducted by researchers from Bar-Ilan University’s Health and Environment Research Lab and included collaborators from Rabin Medical Center, Tel Aviv University, the Hebrew University of Jerusalem and the Alfred Wegener Institute in Germany.
It was funded by the Ihel Foundation and supported by the Israel Science Foundation, the Dorothy and Harold Greenwald Foundation Memorial Prize, Google Research, Bar-Ilan University’s Data Science and AI Institute, the Helmholtz Visiting Researcher Grant and a German-Israeli data-science exchange program.
