Prevalence of gestational diabetes mellitus – do the new WHO criteria make a difference?

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Abstract
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 7.0 mmol/l or 2 h glucose 7.8 mmol/l). Of these 379 cases, only 21 (5.5%) had hyperglycaemia in the range considered diabetes mellitus outside pregnancy (fasting glucose 7.0 mmol/l or 2 h glucose 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 7.8 mmol/l and < 11.1 mmol/l). Using the 1985 criteria (fasting or 2 h glucose 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.