UmbrelLACT Study: Clinical Lactation Study on the Exposure to Medicines Via 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.