Human Milk

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.