Aims: To describe the prevalence of gestational diabetes mellitus (GDM) according to the 1998 WHO provisional recommendations and compare it to that found with previous 1985 WHO criteria.
Methods: A total of 5564 consecutive women aged 20 years or more without diagnosis of diabetes mellitus outside of pregnancy in general prenatal care clinics of the National Health Service in 6 state capitals of Brazil, between their 20th and 28th gestational weeks were enrolled.
Results: Of the 5004 women who completed a 75-g oral glucose tolerance test, 379 (7.6%, 95% confidence interval (CI) 6.9% to 8.4%) had GDM by the 1998 criteria (fasting glucose > or = 7.0 mmol/l or 2 h glucose > or = 7.8 mmol/l). Of these 379 cases, only 21 (5.5%) had hyperglycaemia in the range considered diabetes mellitus outside pregnancy (fasting glucose > or = 7.0 mmol/l or 2 h glucose > or = 11.1 mmol/l); the remaining 358 (94.5%) had hyperglycaemia in the impaired glucose tolerance range (fasting glucose < 7.0 and 2 h glucose > or = 7.8 mmol/l and < 11.1 mmol/l). Using the 1985 criteria (fasting or 2 h glucose > or = 7.8 mmol/l), 378 cases of GDM were found, 15 in the diabetes range and 363 in the impaired glucose tolerance range.
Conclusions: Prevalence of GDM is minimally altered by the new WHO definition. Although GDM is a common condition, the vast majority of the cases have hyperglycaemia in the range considered impaired glucose tolerance outside pregnancy.