Mothers breastfeeding their babies directly rather than use infant formula or expressed breastmilk may be better protecting their children from asthma, according to research from CHILD Study.

The research published this week in The Journal of Pediatrics found that children who were exclusively fed at the breast until they were three-years-old had the lowest risk of asthma.

“It is increasingly common for infants to be fed expressed breast milk, especially in countries that do not offer paid maternity leave,” lead researcher and University of Manitoba assistant professor Meghan Azad said in a release.

The study looked at data from 2,534 infants and their mothers. The infants were classified into four categories once they reached three months of age: breastmilk only (all direct breastfeeding), breastmilk only (some expressed breastmilk), infant formula and breastmilk, and formula only.