“Some of these bacteria come from mother's skin and are usually harmless at normal levels. But coliform and salmonella could be coming from elsewhere,” Keim said. “We know from another study that about two-thirds of women who use a breast pump never wash” its parts, she said.
While certain bacteria are natural components of breast milk and are healthy for the baby, abnormal levels of some types of bacteria, and contamination with disease-causing bacteria could be dangerous to infants, especially those who were born pre-mature or have weak immune systems, the researchers said. A previous study showed about 20 percent of people looking online for breast milk mention they have a baby who was born pre-mature or has a health condition.
The results also showed that each additional transit day was associated with an increase in total bacteria count in milk purchased online.
There are other avenues for risk as well, the researchers said. Women who are lactating and selling their extra milk could be using medications, or could be exposed to chemicals because of their occupation, some of which could find their way into the milk.