Human Milk

Preterm infants are at increased risk of vitamin A deficiency because they are born with low vitamin A stores and depend largely on breast milk to meet their nutritional needs. This study will evaluate whether daily maternal vitamin A supplementation increases vitamin A concentrations in the breast milk of mothers who deliver infants before 29 weeks of gestation. Participants will receive a commercially available oral multivitamin supplement containing 1,300 mcg retinol activity equivalents (RAE) of vitamin A daily for four months after delivery. Breast milk samples will be collected at 2 weeks, 2 months, and 4 months postpartum to measure vitamin A concentrations. The study will assess whether maternal supplementation is a feasible approach for increasing breast milk vitamin A concentrations in mothers of preterm infants.

The goal of this observational study is to determine the concentration of medicines in human milk during maternal medicine intake. The main questions it aims to answer are: * What is the concentration of maternal medicines in human milk? * What is the (estimated) intake and exposure in the breastfed infant? Participants will be asked to * fill out a questionnaire regarding medical data of the mother and child * track medication intake for 3 days * collect milk samples during 24 hours * optionally, donate 2 blood samples of the mother and give consent to one blood sample of the child * fill out a questionnaire regarding the general health of the child.