The risk of postpartum maternal hyperglycaemia in women with gestational diabetes is reduced by breastfeeding

Abstract

Background and aims: Gestational diabetes (GDM) is associated with adverse fetal and maternal outcomes. It identifies women at risk of pre-diabetes, type 2 diabetes (T2DM) and cardiovascular risk in later life. Recent studies have suggested that breastfeeding may confer a beneficial effect on postpartum maternal glucose tolerance in both women with GDM and normal glucose tolerance (NGT) in pregnancy. Materials and methods: We compared results from 300 women with GDM and 220 women with NGT according to IADPSG criteria using a 75g oral glucose tolerance test (OGTT) at 24-28 weeks gestation by repeating the 75g OGTT postpartum to reassess glucose status. We also tested for postpartum metabolic syndrome (MetS) according to international criteria. Binary logistic regression was used to identify maternal factors that increased the risk of persistent glucose intolerance. Postpartum lactation status was categorised as breastfeeding alone, bottle-feeding alone, or both. Results: 520 women were tested. OGTT results were classified as normal (FPG<5.6mmol/l; 2h<7.8mmol/l) or abnormal (IFG; 5.6-6.9, IGT; 2h 7.8-11.0, IFG+IGT; T2DM FPG≥7 ± 2h≥11.1). Six of 220 (2.7%) women with NGT in pregnancy had postpartum dysglycaemia compared to 57 of 300 women (19%) with GDM in pregnancy (P<0.001). Non-Caucasian ethnicity (OR 3.40, 95% CI 1.45-8.02, P=0.005), family history of T2DM (OR 2.14, 95% CI 1.06-4.32, P=0.034) and insulin use in pregnancy (OR 2.62, 95% CI 1.17-5.87, P=0.019) were all predictive of persistent dysglycaemia. MetS was present postpartum in 31 of 300 women (10.3%) with GDM compared to 18 (8.2%) of 220 women with NGT (P=0.4). The prevalence of persistent dysglycaemia was lower in women who breast-fed versus bottle-fed their babies, or employed both techniques (7.1% v 18.4% and 11.2%, respectively, p<0.001). Conclusion: In this Irish population the prevalence of persistent glucose intolerance in women with GDM in pregnancy is 19% compared to 2.7% in NGT women. Breast-feeding confers a beneficial effect on postpartum glucose tolerance. The precise mechanism behind this association is unclear and requires further study.