Background
Type 2 Diabetes Mellitus (T2DM) affects approximately 500 million adults worldwide(1). The pharmacotherapy of T2DM reduces risk of morbidity and mortality(2), however only about 10% of clinically approved medications have any information on use in pregnant and lactating women(3). WHO recommends initiation of breastfeeding within the first hour of birth and exclusive breastfeeding for the first six months of life(4). Ambiguity remains around the safety of taking T2DM medication whilst breastfeeding that makes it hard for women with T2DM to safely adhere to this guidance.
Methods
A list of drug therapies for treating T2DM was generated from national and international clinical guidelines. A systematic search of research articles reporting human plasma and breastmilk drug concentrations was conducted in Scopus, PubMed, Google Scholar, and LactMed® in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies evaluating breastmilk drug transfer in T2DM, with fully accessible abstract and main text reported in English were included. Study quality was evaluated using the ClinPK checklist. Authors evaluated clinical guideline recommendations on the use of T2DM drugs in lactation, and the basis upon which such recommendations were made.
Results
Only five out of 20 drugs (Metformin, Glyburide, Glipizide, Tolbutamide, and Semaglutide) have clinical data on plasma-to-breast milk transfer. Metformin and Tolbutamide were detectable in maternal plasma and breastmilk. Half (51.7%) of guideline recommendations provide explicit guidance. Only 4.4% of recommendations were based on clinical evidence. Over half (57.8%) of recommendations were accessible online, and most guidelines recommendations (78%) were against the use of anti-glycaemic agents whilst breastfeeding.
Conclusion
The scarce clinical evidence to guide T2DM drug therapy during breastfeeding available has several design and methodological limitations. Published recommendations remain largely inconsistent, thus perpetuating uncertainty in the use of T2DM drug therapies in lactation. Addressing knowledge gaps is critical in developing clinical consensus to optimize T2DM drug therapy among breastfeeding mothers.
References
- Ong KL, Stafford LK, McLaughlin SA, et al. Global, regional, and national burden of diabetes from 1990 to 2021, with projections of prevalence to 2050: a systematic analysis for the Global Burden of Disease Study 2021. Lancet. 2023;402(10397):203-234. doi:10.1016/S0140-6736(23)01301-6
- Odom EC, Li R, Scanlon KS, Perrine CG, Grummer-Strawn L. Reasons for earlier than desired cessation of breastfeeding. Pediatrics. 2013;131(3):e726-e732.
- Mazer-Amirshahi M, Samiee-Zafarghandy S, Gray G, van den Anker JN. Trends in pregnancy labeling and data quality for US-approved pharmaceuticals. Am J Obstet Gynecol. 2014;211(6):690.e1-690.e11.
- World Health Organization. Breastfeeding. 2020. Accessed April 15, 2025. https://www.who.int/data/nutrition/tracking-tool/breastfeeding
