Association of lactation with maternal risk of type 2 diabetes – a systematic review and meta‐analysis of observational studies

Aims To investigate the association between lactation and maternal risk of type 2 diabetes, including a potential graded association according to lactation duration. Methods Systematic review and meta-analysis of observational studies that investigated the reported association between lactation (irrespective of duration, intensity or mode) on maternal risk of type 2 diabetes. Results A total of 21 studies (17 cohort studies and 5 cross-sectional studies) were included in this systematic review, and 16 contributed to the meta-analysis. Studies that investigated the association of lactation with risk of type 2 diabetes in the first months after birth in women with gestational diabetes reported conflicting results. Studies with longer follow-up showed a graded protective association for lactation and risk of type 2 diabetes, with a potentially larger risk reduction in women with gestational diabetes than in those without gestational diabetes. Overall, ever versus never lactation was associated with a 27% lower risk of type 2 diabetes (RR 0.73, 95% CI [0.65, 0.83]). Each additional month of lactation was associated with a 1% lower risk of type 2 diabetes (RR 0.99, 95% CI [0.98, 0.99]). However, the overall quality of the studies was modest. Conclusions Lactation is associated with a significantly reduced risk of maternal type 2 diabetes over the life course, particularly in women with gestational diabetes. The protective effect seems to increase with longer duration of lactation. Further research is warranted to understand whether this association is modified by exposure to other risk factors. This article is protected by copyright. All rights reserved.