Mommy’s Milk is looking for lactating parents who are currently nursing an infant who is less than 6 months old to join a research study examining the diversity of human milk. 480 nursing parents/babies will be enrolled in the first phase of the study, which includes receiving weekly text messages inquiring about use of any prescription antibiotics and/or changes in lactation status.

Based on the responses to the weekly text message, we will then invite a subset of nursing parents/babies to participate in the second phase of the study. This phase will include 40 nursing parents who are prescribed certain antibiotics while they are still nursing, plus two comparison groups: 20 parents who are prescribed an antibiotic but are no longer nursing and 40 nursing parents without antibiotic exposure.

See Additional Details below for a list of all Phase 1 and Phase 2 study activities.

The goal of the study is to learn whether antibiotics, when taken by a lactating parent, can be found in human milk, other biological samples from the parent and/or baby, or environmental samples collected in the home, and whether this has any effect on an infant’s growth or development. Please consider joining our study so we can learn more about the diversity of human milk!

Sign Up – Diversity of Human Milk

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You are eligible to participate if you are:

  • 18+ years of age
  • Currently living in Southern California
  • Nursing an infant 6 months old or younger
  • Have access to an electric pump to express milk

You’ll be asked to:

  • Provide self-collected milk samples, self-collected stool samples and skin swabs from both the nursing parent and nursing baby, and self-collected surface swabs taken from specific areas of your home. Collection kits will be provided for all samples.
    • Parents/babies participating only in Phase 1 of the study will be asked to provide these samples just one time.
    • Parents/babies who go on to participate in Phase 2 of the study will be asked to provide these samples up to 3 additional times.
  • Participate in phone interviews
  • Complete questionnaires about your baby’s development up to 12 months of age
  • Release your and your baby’s medical records
  • Respond to weekly text messages asking about any new antibiotic prescriptions and/or any changes in lactation status (Phase 1 study participants only)


  • Volunteers in Phase 1 of the study will receive a $20 gift card to compensate them for their time spent in study activities.
  • Volunteers in Phase 2 of the study will receive a $10 gift card to compensate them for their time each time they are asked to provide additional samples.

For more information, please contact Mommy’s Milk by email at or call 858.246.1713.