Introduction: During the years 2014-2015 new diagnostic criteria for gestational diabetes mellitus (GDM) were gradually adopted by the Czech professional societies, which emerged from the results of the large prospective multicenter HAPO study (The Hyperglycemia and Adverse Pregnancy Outcome). The adoption of the new criteria was accompanied by concerns about the increase in the number of women with GDM. The paper deals with epidemiological results of GDM incidence in the first three years since the introduction of new criteria.
Methods and results: In the years 2013-2014 GDM screening was performed at 1,594 pregnant woman at the General Teaching Hospital in Prague. According to that time valid diagnostic criteria (fasting glucose 5.6 mmol/g and/or 8.9 mmol/l in 60 min and/or 7.7 mmol/l in 120 min 75 g OGTT) GDM was found in 324, i.e. 20 % of women. In the years 2016-2018 were 2,629 pregnant women examined. GDM based on the new criteria (fasting blood glucose 5.1 mmol/l and/or 10 mmol/l in 60 min and/or 8.5 mmol/l in 120 min OGTT) was diagnosed in significantly less women - in 375, i.e. 14.3% (p < 0.0001). Overt diabetes, i.e. fasting glucose 7.0 mmol/l and/or 11.1 mmol/l in 120 min OGTT, was newly detected in 6 pregnant women, i.e. 0.2 %. Gestational diabetes was found in 62% cases based on repeated fasting fasting blood glucose and in 38% on the basis of higher blood glucose at 60 min and/or 120 min OGTT. GDM was significantly more prevalent in the age category over 30 years. Among women aged under 25 years GDM was present at 9.9%, aged 25-29.9 years at 9.6%, aged 30-34.9 years at 14.2% and aged 35 years at 18.6 %. Hypoglycaemia < 3.5 mmol/l experienced 2.9% of women during OGTT. When the screening in 2016-2018 was evaluated according to the previous diagnostic criteria, diabetes would be diagnosed in 16.2% of pregnant women. The result of the test would be falsely negative in 6% of all pregnant women, i.e. these women have repeatedly higher fasting glucose (5.1-5.5 mmol/l) according to the current criteria which was evaluated as physiological according to the previous criteria. However, in the HAPO, these values were already associated with a significant increase of complications. A total of 50% of women with GDM diagnosed according to the previous criteria would have a false positive result of OGTT (8.9-9.9 mmol/l in 60 min and/or 7.7-8.4 mmol/l in 120 min OGTT). These values are not considered to be significantly at risk under the new criteria.
Conclusion: Our data do not confirm the increase in GDM incidence following the introduction of new diagnostic criteria which, according to current knowledge, better reflect the real risks of complications for the child and the mother. Applying the previous criteria has led to a number of false negative and positive results, so we consider the adoption of better-funded new criteria a step in the right direction. The incidence of diabetes was significant in all age categories and significantly increased in women over 30 years of age.
Keywords: HAPO study; IADPSG; diagnostic criteria; gestational diabetes mellitus; screening.