Reliable information on medicine safety during breastfeeding is lacking for many medications. In order to avoid the risk of harming the baby, mothers taking medication for various diseases may be advised by their doctor to discontinue the medication during breastfeeding (or the woman herself may choose to discontinue). Alternatively, the woman may be advised to continue the medication but refrain from breastfeeding. Both options are unfortunate. The mother needs the prescribed medication and breastfeeding has benefits for both the baby and the mother.
Why is there a lack of reliable information on medicine safety during breastfeeding? This is because breastfeeding mothers are usually excluded from clinical studies. Therefore, there is limited knowledge of the extent to which different drugs are transferred to the baby via breast milk. The lack of reliable safety information applies to both already approved and new drugs. However, since many mothers take medications while breastfeeding, it should be possible to establish lactation studies that systematically provide scientific evidence for better safety information. Which drugs can be used during breastfeeding?
A new article with Mats G. Hansson as lead author and Erica Sundell as one of the co-authors describes how, within the framework of current regulatory requirements, two breastfeeding studies have been started that can help solve the dilemma that breastfeeding mothers and their doctors often face. One study concerns a drug for diabetes, the other a drug for inflammation and rheumatic disorders. The studies are part of the European project ConcePTION, which will produce evidence on drug safety during pregnancy and breastfeeding. Breast milk samples from the mother and blood samples (plasma) from the mother and child are analyzed to measure how much of the drugs are transferred to the child during breastfeeding. The samples are stored in a biobank for future research, and the studies thus contribute to creating an infrastructure for lactation studies of medicine safety.
Recruitment of research participants and sample collection started in the spring of 2024 and will end at the turn of the year 2025/2026. The purpose of the article is to use the experiences from setting up the two studies as a template for initiating clinical lactation studies. What should be considered? What are the conditions for this type of research? The article concisely describes relevant conditions and procedures for informed consent, sampling, transport and storage of samples, and laboratory analysis. The article also discusses the different conditions for studies of already approved drugs and for new drugs.
The article is important reading for researchers and others who can in one way or another contribute to initiating studies for better information on medicine safety during breastfeeding. Because it so concisely describes the conditions for new studies, the article is also interesting as a concrete example of how problems can be solved by starting new research.
Read the article here: Setting up mother–infant pair lactation studies with biobanking for research according to regulatory requirements.

Written by…
Pär Segerdahl, Associate Professor at the Centre for Research Ethics & Bioethics and editor of the Ethics Blog.
Hansson M, Björkgren I, Svedenkrans J, et al. Setting up mother–infant pair lactation studies with biobanking for research according to regulatory requirements. British Journal of Clinical Pharmacology. 2025; 1-6. https://doi.org/10.1002/bcp.70201
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