Prevalence of gestational diabetes mellitus - do the new WHO criteria makea difference?

Aims To describe the prevalence of gestational diabetes mellitus (GDM) acco rding to the 1998 WHO provisional recommendations and compare it to that fo und with previous 1985 WHO criteria. Methods A total of 5564 consecutive women aged 20 years or more without dia gnosis of diabetes mellitus outside of pregnancy in general prenatal care c linics of the National Health Service in 6 state capitals of Brazil, betwee n 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 greater than or equal to 7.0 mmol/l or 2 h glucos e greater than or equal to 7.8 mmol/l). Of these 379 cases, only 21 (5.5%) had hyperglycaemia in the range considered diabetes mellitus outside pregna ncy (fasting glucose greater than or equal to 7.0 mmol/l or 2 h glucose gre ater than or equal to 11.1 mmol/l); the remaining 358 (94.5%) had hyperglyc aemia in the impaired glucose tolerance range (fasting glucose < 7.0 and 2 h glucose greater than or equal to 7.8 mmol/l and < 11.1 mmol/l). Using the 1985 criteria (fasting or 2 h glucose greater than or equal to 7.8 mmol/l) , 378 cases of GDM were found, 15 in the diabetes range and 363 in the impa ired glucose tolerance range. Conclusions Prevalence of GDM is minimally altered by the new WHO definitio n. Although GDM is a common condition, the vast majority of the cases have hyperglycaemia in the range considered impaired glucose tolerance outside p regnancy.