December 16, 2025, 10:55 am | Read time: 4 minutes

Green surroundings, healthy babies—it seems logical at first. Indeed, previous studies have shown that pregnant women living in greener areas tend to have healthier children. Whether it’s the trees themselves that contribute to healthier babies or if higher income and better healthcare play a bigger role was unclear. Wealthy, educated people tend to prefer living near nature and parks. Researchers at Drexel University in Philadelphia chose a different method to explore this question, and their findings have now been published in the journal “Science of The Total Environment.”¹

What Makes the Study’s Methodology So Special

The study’s results are based on a new experiment. Between 1990 and 2020, 36,000 trees were planted in Portland, Oregon, by a nonprofit environmental organization. These were planted in both poorer and wealthier areas. Thus, the distribution of trees does not correlate with the residents’ social or financial status.

What Was Measured?

The researchers counted 36,564 births that occurred between 2015 and 2020. They also counted how many trees were planted within 100 meters of the mother’s residence in the ten years before a child’s birth. The study considered important factors such as education level, income, ethnicity, and Body Mass Index (BMI). All data were compared with the child’s birth weight. The researchers also considered the occurrence of preterm births.

Each Tree Increases Baby’s Birth Weight

The results showed: Each tree planted within 100 meters in the ten years before birth was associated with an average increase of 2.3 grams in birth weight. If 50 trees were nearby, the babies weighed an average of 50 grams more at birth. “That doesn’t sound like much, but if every baby in our sample gained 50 grams at birth, it means 642 fewer underweight babies,” explains study leader Prof. Yvonne Michael in a university statement.² This, in turn, has positive effects on the child’s development and thus their entire life.

What Exact Influence Do the Trees Have?

Better air, less stress from calming greenery, less sensory overload—researchers suspect that the well-known positive properties of trees on the body and psyche also affect the developing baby in the womb and can even prevent preterm births. For older trees, this is even more true, as their denser foliage can compensate for more pollutants and street noise. They are convinced: The planting initiative has allowed numerous babies to benefit for their entire lives.

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Study Classification

Wealthy people live in green areas. “By focusing on newly planted trees, we were able to reduce this bias—we viewed the situation as a natural experiment,” says Michael. “Additionally, we only included birth data after the trees were planted, establishing a timeline.” The study is currently one of the most precise of its kind, providing detailed information on the impact of trees on newborns’ health. However, the results are from one geographic region and are not directly transferable to other countries. The study also did not consider whether the expectant mother actually stayed at her residence permanently or moved in the meantime. Factors like diet or personal living conditions—which also strongly influence the child’s health—could not be captured in this study. In short: While there is clearly a connection, whether the trees are the main cause cannot be definitively proven.

Can’t Do Without Trees!

Interestingly, it was found that birth weight decreased during the wildfires in 2020. Climate change—according to the researchers—also shows its effects here. The results support another study that Michael and his team published in 2013.³ They found that the loss of 100,000 trees was associated with an increase in deaths from heart and respiratory diseases. Planting trees is never a waste of money.