New Clinical Trials Set Gold Standard for Breastfeeding and Medication Safety: BMJ Study

BMJ Open has published a protocol that sets a new gold standard for clinical lactation studies, addressing the ethical and scientific gaps in understanding drug safety during pregnancy and breastfeeding. The protocol is part of two ongoing clinical trials at Uppsala University’s Centre for Research Ethics & Bioethics.

Women who stop treatment during pregnancy or breastfeeding face a troubling dilemma, as they must weigh their desire to have children and breastfeed against poorly understood health risks.

Currently, 95% of all medicines lack sufficient safety data for use during pregnancy and lactation. Existing standards rely heavily on outdated animal studies and limited data, using pharmacokinetic/pharmacodynamic (PB/PK) models to estimate drug transfer to infants. The new protocol goes further by collecting and analyzing breast milk and plasma samples from both mothers and breastfed infants.

The trials focus on two commonly prescribed medications: prednisolone, used for rheumatoid arthritis, and metformin, used for type 2 diabetes. Samples are biobanked and analyzed for pharmacokinetics and drug transfer levels, with informed consent enabling future research and long-term follow-up on medication effects in infants.

Participants are recruited through clinical centers across Sweden, and samples are stored within a network of breast milk biobanks coordinated by BBMRI-ERIC, embedding the study in a larger European research infrastructure.

This research marks a crucial step toward resolving the ethical and clinical uncertainties faced by pregnant and breastfeeding women, offering a scientifically robust and ethically sound path forward.

“The lack of scientific evidence is an ethical problem for women and doctors, considering that around 70 percent of women need to use medicines sometime during their pregnancy. In many cases, women are recommended to refrain from breastfeeding or stop using their medicines. However, breastfeeding has benefits for both mother and child,” says Mats G. Hansson, senior professor of biomedical ethics at Uppsala University’s Centre for Research Ethics & Bioethics, head of two ongoing clinical trials.

Reference: Svedenkrans J, Hellgren K, Backlund K, et al. Determination of prednisolone concentration in human breast milk and plasma of breastfed infants: study protocol of a Swedish multicenter low-intervention clinical trial, BMJ Open 2025;15:e097898. doi: 10.1136/bmjopen-2024-097898