OBJECTIVE: To assess the association of subsequent pregnancy with subsequent metabolic syndrome and type II diabetes mellitus after a pregnancy complicated by mild gestational diabetes mellitus (GDM). METHODS: We conducted a prospective observational follow-up study of women with mild GDM randomized from 2002 to 2007 to usual care or dietary intervention and glucose self-monitoring. Women were evaluated 5-10 years after the parent study. Participants were grouped according to the number of subsequent pregnancies (group A, none [reference]; group B, one; group C, two or greater). Serum triglycerides, glucose tolerance, high-density lipoprotein cholesterol, blood pressure, and waist circumference were assessed. Metabolic syndrome was diagnosed by American Heart Association and National Heart Lung and Blood Institute criteria. Multivariable regression was used to estimate adjusted relative risks (RRs) and 95% confidence intervals (CIs). RESULTS: Of 905 eligible women from the original trial, 483 agreed to participate, 426 of whom were included in this analysis. Groups A, B, and C consisted of 212, 143, and 71 women, respectively. Of women with subsequent pregnancies, 32% (69/214) had another pregnancy complicated with GDM. No difference between groups was observed for metabolic syndrome (group A, 34%; group B, 33%; group C, 30%). Subsequent pregnancies were associated with diabetes mellitus outside of pregnancy (group A, 5.2%; group B, 10.5%, RR 2.62, 95% CI 1.16-5.91; group C, 11.3%, RR 2.83, 95% CI 1.06-7.59), and if complicated with GDM (no subsequent GDM pregnancy, RR 1.99, 95% CI 0.82-4.84; subsequent GDM pregnancy, RR 3.75, 95% CI 1.60-8.82). CONCLUSION: In women with prior mild GDM, subsequent pregnancies did not increase the frequency of metabolic syndrome, but subsequent pregnancies with GDM increased the risk of diabetes mellitus outside of pregnancy.