A new study offers possible clues to why babies who drink pumped breast milk are at greater risk of asthma, allergies and obesity. Meghan Azad, a senior researcher says the bacterial content differs between milk that was pumped first and milk delivered straight from the breast. The study found that pumped milk was associated with more potential pathogens and lower levels of so-called good or helpful bacteria. In the research, pumped milk was linked to lower levels of bifidobacteria — the type that usually dominates the infant gut and is considered healthy. Meghan Azad, research scientist says "the research only explains less than a third of bacterial variation in breast milk." Other variations could be related to genetics, the home environment, chemicals present in the infant's household, or random causes.