Milk in Life Conditions (MiLC): Bacterial Composition of Human Milk Pumped and Stored in "Real-Life" Conditions

Overview

The MiLC trial is a randomized control trial of two different breast pump set-ups: mother's own and sterile. The objective of this trial is to investigate the bacterial composition of human milk pumped and stored in "real-life" conditions. To meet this objective, lactating mothers will fully express breast milk from one breast on two consecutive pumping sessions at home, once with the participant's own pumps and collection kits (own pump set-up) and once with a hospital-grade pump and disposable, sterile collection kits (sterile pump set-up). Randomization will be used to determine which pump participants use first. From the total volume of milk pumped during each pumping session, the researchers will collect 1 oz. Milk from both pumps will be stored at home and sampled on days 0, 2, 4, and 30 after expression for analysis of its bacterial composition.

Participants will donate 1 oz of human milk during each of two consecutive pumping sessions, for a total volume of 2 oz donated on one day. To collect this human milk, participants will be asked to fully express one breast during each pumping session. Participants will pump once with the participant's own pump set-up and once with the sterile pump set-up (provided by the research team). Women will be randomized to which pump is used first. Randomization will be done using stratified randomization as follows: participants were stratified by how their infants were fed, namely whether infants were fed human milk only vs. human milk and complementary foods). Then, randomization was conducted within each strata. The researchers aim to have a minimum of 25 participants in each stratum. All human milk collections will occur at participants' homes between 0700 and 1100 hours. The second pumping session must begin 3 hours (+/-30 minutes) after the beginning of the first pumping session (e.g. the first pumping session at 7:30 am and the second at 10:30 am). Participants will elect from which breast to donate human milk and that breast will be used for both pumping sessions. Participants will be asked not to nurse from or pump that breast during the 2 hours before the first pumping session and not until after the second pumping session (a total of \~5.5 hours). From the milk produced during each pumping session (which could be up to \~6 oz), researchers will collect 1 oz using a sterile, plastic syringe. Participants will keep the remaining volume of milk. Each ounce of milk collected will be separated into 5 sterile containers (provided). Participants will store donated milk at home until it is picked up by a researcher 2, 4, and 30 days after pumping.