Mother’s milk provides sustenance for babies. Now researchers find pumped breast milk exposes newborns to more disease-causing bacteria than milk directly from the breast. The discovery suggests breastfeeding practices could shift the makeup of microorganisms in breast milk and infants’ digestive systems.

“We were surprised that the method of feeding was the most consistent factor associated with milk microbiota composition,” said Meghan Azad, a medical geneticist at the Children’s Hospit