Risk of diabetes mellitus after pregnancy complicated by gestational diabetes mellitus (GDM)

OBJECTIVES: The aim of the study was an assessment of glucose tolerance disorders' (GTD) prevalence after pregnancy complicated by GDM. DESIGN: Retro- and prospective clinical study. MATERIAL AND METHODS: The group of 461 women having GDM in their index pregnancies was invited to postpartum glucose metabolism assessment. Of them 192 subjects responded positively. In 47 of them the postpartum diagnosis of diabetes had already been established. The remaining 145 subjects underwent detailed testing that embraced fasting plasma glucose and whole blood HbA1c level measurement. Oral 75-g glucose tolerance test (OGTT) was also performed. RESULTS: OGTT revealed GTD in 55 subjects. Diabetes was found in 8 cases, impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) in 23 and 24 cases respectively. Postpartum GTD appeared in 63.3% of insulin treated subjects (GDM2) compared with 30.1% of women treated with diet only (GDM1). A group with pathological OGTT had mean HbA1c concentration significantly higher compared to the one with normal test results (6.0+/-1.7% vs. 5.1+/-0.3%; p<0.001), although HbA1c>6.0% was observed only in 23.6% women with GTD. Moreover, in 25% of subject with newly diagnosed diabetes HbA1c level did not exceeded 6.0%. CONCLUSIONS: 1. More than 50% of subjects with GDM developed diabetes or other GTD during the first 6 years postpartum. 2. Risk of postpartum GTD is significantly higher in women treated with insulin during pregnancy. 3. HbA1c measurement is less sensitive than OGTT for detection of GTD after pregnancy complicated by GDM.