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Background: Several prognostic models for gestational diabetes mellitus (GDM) are provided in the literature; however, their clinical significance has not been thoroughly evaluated, especially with regard to application at early gestation and in accordance with the most recent diagnostic criteria. This external validation study aimed to assess the predictive accuracy of published risk estimation models for the later development of GDM at early pregnancy. Methods: In this cohort study, we prospectively included 1132 pregnant women.Risk evaluation was performed before 16 + 0 weeks of gestation including a routine laboratory examination. Study participants were followed-up until delivery to assess GDM status according to the IADPSG 2010 diagnostic criteria. Fifteen clinical prediction models were calculated according to the published literature. Results: Gestational diabetes mellitus was diagnosed in 239 women, that is 21.1% of the study participants. Discrimination was assessed by the area under the ROC curve and ranged between 60.7% and 76.9%, corresponding to an acceptable accuracy. With some exceptions, calibration performance was poor as most models were developed based on older diagnostic criteria with lower prevalence and therefore tended to underestimate the risk of GDM. The highest variable importance scores were observed for history of GDM and routine laboratory parameters. Conclusions: Most prediction models showed acceptable accuracy in terms of discrimination but lacked in calibration, which was strongly dependent on study settings. Simple biochemical variables such as fasting glucose, HbA1c and triglycerides can improve risk prediction. One model consisting of clinical and laboratory parameters showed satisfactory accuracy and could be used for further investigations.

Women with a history of gestational diabetes mellitus (GDM) are at high risk of developing hyperglycemia in a subsequent pregnancy. This study aimed to assess parameters of glucose metabolism at the beginning of a subsequent pregnancy in women with a history of GDM. This prospective cohort study included 706 women who had at least one previous pregnancy (120 with prior GDM and 586 without GDM history). All study participants received a broad risk evaluation and laboratory testing at the beginning of a subsequent pregnancy and were followed up until delivery to assess GDM status, risk factors for GDM recurrence, and pregnancy outcomes. Women with a history of GDM exhibited lower insulin sensitivity and subtle impairments in β-cell function associated with subclinical hyperglycemia already at the beginning of a subsequent pregnancy compared to women without GDM history. This was associated with a markedly increased risk for the later development of GDM (OR: 6.59, 95% CI 4.34 to 10.09, p < 0.001). Early gestational fasting glucose and HbA1c were identified as the most important predictors. Mothers with a history of GDM showed marked alterations in glucose metabolism at the beginning of a subsequent pregnancy, which explains the high prevalence of GDM recurrence in these women.