Exclusion criteria included previous GDM plus women on insulin therapy or oral hypoglycaemic agents (OHA) for four studies [33, 38–40], only women on insulin therapy or OHAs with no reference to previous GDM for two studies [26, 28], previous GDM and women on insulin therapy for one study [35], only women with previous GDM for one study [37], only women on insulin therapy for one study [41], T1DM or T2DM and insulin therapy for three studies [27, 32, 36] and only T1DM or T2DM for one study [42]. Here, INS is linked to type 2 diabetes mellitus.