More than 1.5 million babies are born prematurely worldwide with breathing problems because their lungs do not have a chance to fully develop, according to the World Health Organization. 

Previous studies on children have indicated that these children are also at a higher risk of asthma later on in life. However, a new study, published in the journal PLoS Medicine, has found that the risk is even higher than previously thought.

Using 30 studies from six different continents, researchers looked at thousands of babies born since the 1990s. What they found was that, despite improved care for preterm infants, the risk of asthma for children born early (37 weeks or earlier) is significantly higher than children who are born full-term.

Overall, asthma was found to affect 8% of all children born full-term and 14% of all babies born prematurely; that’s nearly double the risk! In detail, babies born before 37 weeks were 50% more likely to develop asthma, and those born three months early were three times more likely to develop asthma than those born full-term. Moreover, children at risk for developing the condition were the same among preschool aged children, which suggests they don’t outgrow their risk over time.