Pregnant women who live in greener neighborhoods may have lower levels of long-term stress, according to a new study led by researchers from Bar-Ilan University. The study found that greater exposure to residential greenery during pregnancy was associated with lower levels of cortisol and cortisone -- two key stress hormones that can affect both maternal and fetal health.
Unlike stress hormones measured in blood, saliva, or urine, which reflect stress over minutes or hours, hormones measured in hair provide a profile of stress hormones accumulated over several months. By analyzing hair samples from hundreds of pregnant women, the researchers were able to assess chronic stress levels during the second trimester of pregnancy.
Published in Environmental Epidemiology , the study 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.
“Our findings suggest that exposure to greenery around the home is associated with reduced chronic stress hormones during pregnancy,” said Sohini Bhattacharya , a PhD candidate from the Azrieli Faculty of Medicine of Bar-Ilan University who investigated the links. “This is important because prolonged exposure to elevated stress hormones can negatively affect both the mother and the developing fetus.”
The study included 385 pregnant women recruited from the Helen Schneider Hospital for Women at Rabin Medical Center in Petah Tikva, Israel. Researchers collected hair samples and analyzed hormone levels using advanced laboratory techniques.
To estimate exposure to greenery, the team used two complementary approaches. First, they measured vegetation around participants’ homes using satellite imagery and the widely used Normalized Difference Vegetation Index (NDVI). They then applied a novel method based on Google Street View images, allowing them to assess greenery from a pedestrian’s perspective and distinguish between different types of vegetation, including grass, trees, and other plants.
Both methods pointed to the same conclusion: women living in greener surroundings had lower long-term stress hormone levels.
One of the study’s most unexpected findings emerged from the street-level analysis. Women living in areas with a higher percentage of grass around their homes had notably lower cortisol and cortisone levels than women living in less grassy environments.
This finding may have practical implications for urban planners and policymakers seeking cost-effective ways to improve public health and well-being.
Stress hormones such as cortisol and cortisone play important roles in regulating metabolism, immune function, sleep cycles, and maintaining pregnancy. However, prolonged elevation of these hormones can be harmful.
Previous studies suggested that exposure to natural environments may reduce stress, but most relied on self-reported measures or short-term biological indicators. Few studies have examined long-term stress using hair samples, and even fewer have focused specifically on pregnant women.
The current study builds on earlier research by the same team, which found an association between residential greenness and lower hair cortisol levels during the first trimester of pregnancy. The new study expands those findings by examining additional hormones, later stages of pregnancy, and more detailed measures of greenery.
The findings come at a time when many populations, including those in Israel, are experiencing increased stress due to ongoing conflict, climate change, and rapid urbanization. Pregnant women are particularly vulnerable to the health effects of chronic stress.
The lead researcher of the study, Prof. Keren Agay-Shay , from the Azrieli Faculty of Medicine of Bar-Ilan University, says, “Our findings support efforts to preserve and expand green spaces and greenness in residential neighborhoods. 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 research team is continuing to investigate environmental factors that may affect hormone levels during pregnancy, including exposure to air pollution and temperature.
This research was funded by the Ihel Foundation and supported in part by the Israel Science Foundation (ISF Grant No. 184/19), the Dorothy and Harold Greenwald Foundation Memorial Prize, Google Research, the Data Science and AI Institute at Bar-Ilan University, the Helmholtz Visiting Researcher Grant, and the Helmholtz Information and Data Science Academy (HIDA) and Israel Data Science Initiative (IDSI) exchange program.
The study was led by researchers from the Health and Environment Research (HER) Lab at Bar-Ilan University’s Azrieli Faculty of Medicine and involved collaborators from Bar-Ilan University, Rabin Medical Center, Tel Aviv University, the Hebrew University of Jerusalem, and the Alfred Wegener Institute in Germany.
Environmental Epidemiology
Satellite and ground-level residential greenness and hair steroid hormones during pregnancy
1-Jun-2026