Sources of Bacterial Contamination in Human Milk Samples From the MiLC Trial

Participants donated HM from two consecutive pumping sessions at home. Women pumped once with their own pump and milk collection kit, and once with a sterile and sterile collection kit. Both pumping sessions occurred at participants' homes between 0700 and 1100 hours. The second pumping session occurred within 3 hr (+/- 30 min) after the beginning of the first. Randomization was used to determine which pump was used first. Women elected from which breast they donated their HM and were asked not to nurse on that side 2 hr before the first pumping session and not until after the second. Before women pumped with their own pump, swabs were taken of the breast from which HM was donated, the women's dominant hand, their own bottle/flange, their own pumps (port of pump and tubing), and their babies' mouths.

There was only one group but stratified enrollment was used to ensure equal numbers of women whose infants consumed HM only and women whose infants consumed HM and complementary foods.