Sodium Awareness in Lactation Trial

Inclusion Criteria: 1. Consent provided 2. Have delivered a preterm singleton or twin infant at \<35 weeks gestation admitted to a study NICU at birth or transferred into a study NICU from another NICU within the first 72 hours postpartum 3. Day 5 or less postpartum (Day 1 = day of delivery) upon enrollment (ideally day 3 or less) 4. Plans to lactate at least 2 weeks and initiate lactation with a breast pump 5. Expected infant NICU stay of 7+ (ideally 14+) days in enrollment NICU(s) Exclusion Criteria: 1. Potential study participant's infant is critically ill and not expected to survive or has lethal diagnosis with plans by medical team/family to redirect care 2. Has delivered triplets or higher order multiples (potential confounder for lactation challenges; of note, triplets or higher are rare, on the order of a few parents annually) 3. Lactation contraindication(s) (i.e., active chemotherapy) or declines lactation initiation 4. History of breast surgery that may affect ability to lactate (i.e., breast reduction; breast augmentation that utilized nipple incisions) 5. Using or planning to use hormonal birth control in the first 14 days post-partum as may affect secretory activation/lactation 6. Unable/unwilling to be present in study NICU during any of first 5 days postpartum 7. Presumption by the medical team that infant will be in study NICU for \<5 days