According to a new report, increased exposure to sunshine during the second trimester of pregnancy lowers the child’s likelihood of developing asthma.

This report comes not from a group of scientists but from economists at the University of Kansas. They heard about a hypothesis by physicians and Harvard professors Augusto Litonjua and Scott Weiss that suggested vitamin D levels during the second trimester would “influence the probability that a fetus will develop asthma later in life.” So the economists decided to put the hypothesis to the test, using health data, weather data, and surveys.

They looked at when and where asthmatics were born, then looked back even further to see what the weather would have been like in that area when the asthmatics’ mothers were in their second trimester. “If that place is relatively more sunny during the second trimester, we found relatively lower rates of asthma,” said David Slusky, assistant professor of economics at the University of Kansas.

Their report suggests that spending 10 minutes in the sun every day to soak up some vitamin D could help pregnant mothers lessen their child’s likelihood of developing asthma. That being said, many prenatal vitamins already include vitamin D. Nonetheless, sunshine is free and could save our health system, and parents, the cost of dealing with asthma later on.