Lactation and progression to type 2 diabetes in patients with gestational diabetes mellitus: A systematic review and meta-analysis of cohort studies

Aims/Introduction To explore the association between lactation and type 2 diabetes incidence in women with prior gestational diabetes. Materials and Methods We searched PubMed, Embase and the Cochrane Library for cohort studies published through 12 June 2017 that evaluated the effect of lactation on the development of type 2 diabetes in women with prior gestational diabetes. A random effects model was used to estimate relative risks (RRs) with 95% confidence intervals (CIs). Results A total of 13 cohort studies were included in the meta-analysis. The pooled result suggested that compared with no lactation, lactation was significantly associated with a lower risk of type 2 diabetes (RR 0.66, 95% CI 0.48-0.90, I-2 = 72.8%, P < 0.001). This relationship was prominent in a study carried out in the USA (RR 0.66, 95% CI 0.43-0.99), regardless of study design (prospective design RR 0.56, 95% CI 0.41-0.76; retrospective design RR 0.63, 95% CI 0.40-0.99), smaller sample size (RR 0.52, 95% CI 0.30-0.92, P = 0.024) and follow-up duration >1 years (RR 0.75, 95% CI 0.56-1.00), and the study used adjusted data (RR 0.69, 95% CI 0.50-0.94). Finally, by pooling data from three studies, we failed to show that compared with no lactation, long-term lactation (>1 to 3 months postpartum) was associated with the type 2 diabetes risk (RR 0.69, 95% CI 0.41-1.17). Conclusions The present meta-analysis showed that lactation was associated with a lower risk of type 2 diabetes in women with prior gestational diabetes. Furthermore, no significant relationship between long-term lactation and type 2 diabetes risk was detected. The impact of long-term lactation and the risk of type 2 diabetes should be verified in further large-scale studies.