London - Babies fed milk expressed with a breast pump may be at a higher risk of asthma, research suggests.
This is because potentially harmful bacteria found on the surface of pumps could end up in the mother's milk.
A study found those who exclusively breastfeed are more likely to produce milk containing "good" bacteria.
But those who express milk have higher levels of two potentially harmful bacteria, according to researchers from the University of Manitoba in Canada. These may cause changes in a baby's gut bacteria linked to asthma.
Previous research has shown that 12.5 percent of babies fed using a breast pump develop asthma by their third birthday. This compares with 8.8 percent of babies exclusively breastfed.