Using a breast pump can introduce the “wrong” kind of bacteria into babies and increase their risk of childhood asthma, a study suggests.
Researchers found milk from the devices contained higher levels of potentially harmful bugs than “directly fed” breast milk.
At the same time, the proportion of bacteria transferred from the baby’s mouth during natural breastfeeding was reduced.
Increasing evidence suggests this “oral” bacteria contributes to a healthy gut “microbiome”, or microbial community, in babies.
Canadian lead scientist Dr Shirin Moossavi, from the University of Manitoba, said: “Increased exposure to potential pathogens in breast milk could pose a risk of respiratory infection in the infant, potentially explaining why infants fed pumped milk are at increased risk for paediatric asthma compared to those fed exclusively at the breast.”
Once considered sterile, breast milk is now known to contain a complex cocktail of bacteria that may be important in establishing a thriving population of “friendly” bugs in the infant gastrointestinal tract.
Disruption to the infant microbiome could leave a child vulnerable to allergies, asthma or obesity, experts believe.
However the pathways through which bacteria become established in the infant gut have not been clear.
Bugs from the mother carried in breast milk is one probable route, but so is the transfer of mouth bacteria from the mouth of a sucking baby.
Breast pumps offer a third, artificial pathway – one that can potentially transmit a range of environmental bacteria to the baby.
For the study, the researchers looked for bacterial genes in breast milk samples from 393 healthy mothers three to four months after giving birth.
The team found the bacterial content of milk being fed to the mothers’ babies differed greatly from infant to infant.
Milk administered from breast pumps contained higher levels of potentially harmful “opportunistic pathogens” such as Stenotrophomonas and Pseudomonadaceae.
In contrast direct breastfeeding without a pump was associated with microbes typically found in the mouth, as well as greater bacterial richness and diversity.
The research is published in the journal Cell Host & Microbe.
Senior author Dr Meghan Azad, from the Children’s Hospital Research Institute of Manitoba, said: “This study considerably expands our understanding of the human milk microbiota and the factors that might influence it.
“The results will inspire new research about breastfeeding and human milk, especially related to pumping.”
The new evidence suggests infant mouth microbes play an important role in determining what kind of bacteria are found in mothers’ milk, said the scientists.