Inclusion Criteria:

• * Possess a refrigerator with a freezer or a standalone freezer for sample storage at home.
• * Ability to be contacted by telephone.
• * Having internet access at home.
• * Being in the immediate (0-14 days) postpartum period.
• * Currently breastfeeding or planning to breastfeed, regardless of the type.

Exclusion Criteria:

• * Newborns with congenital malformations.
• * Newborns with birth weights less than 2,500g or greater than 4,000g.
• * Gestational age less than 37 completed weeks or greater than 42 completed weeks.
• * Mothers hospitalized in an intensive care unit (ICU).
• * Newborns hospitalized in the neonatal intensive care unit (NICU) or special care nursery (SCN).
• * Mothers using sleep aids (e.g., Benadryl, Unisom, Melatonin, Valerian).
• * Mothers currently being treated for pharmacologically treated mood and sleep disorders.
• * Mothers with acute infections longer than 7 days postpartum. Mothers will be withdrawn from study if antibiotics are taken between 7 and 14 days postpartum.