We assessed whether the insulinogenic index (a measure of early-phase insulin secretion) or the Matsuda index (a measure of insulin sensitivity) at 6 weeks postpartum was associated with T2DM at any time point.<h4>Results</h4>Of 100 women [median age 28 years (IQR 25-32), BMI 27.6 kg/m<sup>2</sup> (IQR 23.8-30.6) at 6 weeks postpartum], 42% (39) developed T2DM by 1 year postpartum. This evidence concerns the gene INS and type 2 diabetes mellitus.