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Proposed Gestational Diabetes Criteria Raise Questions, Concerns


 

From the Annual Meeting of the European Association for the Study of Diabetes

LISBON – Use of the recently proposed International Association of Diabetes and Pregnancy Study Group criteria for identifying women with gestational diabetes would increase the diagnosis by 240%, compared with the World Health Organization's criteria, according to the findings of a population-based multiethnic cohort study of 823 healthy pregnant women in Norway.

“Before endorsing the IADPSG criteria, the impact of diagnosing nearly one-third of all pregnant women should be considered,” said Dr. Kjersti Morkrid of the department of endocrinology at Oslo University Hospital and the Institute of Clinical Medicine at the University of Oslo.

The IADPSG criteria were derived from an international workshop held in Pasadena, Calif., in which 225 conferees from 40 countries reviewed the results of the HAPO (Hyperglycemia and Adverse Pregnancy Outcome) study and other data suggesting that there is a risk for adverse fetal outcomes below current gestational diabetes mellitus (GDM) diagnostic thresholds. Indeed, currently used criteria were either chosen to identify women at risk for the later development of diabetes (Diabetes Care 2007;30:[Suppl. 2]:S251-60), or were derived from nonpregnant individuals (World Health Org. Tech. Rep. Ser. 1980;646:1-80) and were not primarily aimed at identifying pregnancies with increased risk for adverse perinatal outcome, the IADPSG authors noted (Diabetes Care 2010;33:676-91).

The newly proposed criteria, which have been endorsed by the American Diabetes Association but not the American College of Obstetricians and Gynecologists (ACOG), were aimed at identifying women who have a 75% increased risk for adverse fetal outcomes, including birth weight greater than the 90th percentile, primary cesarean delivery, neonatal hypoglycemia, and cord C-peptide above the 90th percentile (the primary HAPO outcomes).

The IADPSG criteria call for an initial measurement of fasting plasma glucose (FPG), random glucose, or hemoglobin A1c level in all or just high-risk women at the first prenatal visit. If the results do not detect overt diabetes but the FPG is 92-126 mg/dL, then GDM is diagnosed. If the FPG is less than 92 mg/dL, then a single 75-g, 2-hour oral glucose tolerance test (OGTT) is performed at 24-28 weeks' gestation. The OGTT should be performed after an overnight fast, with overt diabetes diagnosed if the fasting plasma glucose level is at least 126 mg/dL. GDM is diagnosed if the FPG is greater than 92 mg/dL, if the 1-hour value exceeds 180 mg/dL, or if the 2-hour value exceeds 153 mg/dL.

The IADPSG authors acknowledged that the criteria would “substantially increase the frequency of hyperglycemic disorders in pregnancy,” compared with other criteria such as those of the World Health Organization, which diagnose GDM at 24-28 weeks by either an FPG of at least 126 mg/dL or a 2-hour value of at least 140 mg/dL or higher following a 75-g glucose load.

The Norwegian Stork Groruddalen Research Program quantified that increase in a multiethnic population, including 41% of the 823 from Scandinavia, 24% from South Asia (primarily Pakistan and Sri Lanka), and 15% from the Middle East (mainly from Iraq, Morocco, and Turkey), as well as others from Eastern Europe, East Asia, Somalia, sub-Saharan Africa, and South America.

Compared with women from Scandinavia, those of South Asian and Middle Eastern origin were significantly younger on average (aged 28 and 29 years, respectively, vs. 30 years for Scandinavian women). South Asian women had lower prepregnancy body mass indexes compared with Scandinavian women (23.7 vs. 24.6 kg/m

Of the 759 women who completed the OGTT at visit 2, GDM prevalence rates were 32% by the IADPSG criteria, compared with just 13% by the WHO criteria. The overall increase in GDM diagnosis was by a factor of 2.4, ranging from 2.2 for Scandinavian and Middle Eastern women to a 2.8-fold increase among Southeast Asian women.

There was poor overlap between the two criteria, with just 9% identified by both, 4% by only the WHO criteria, and 22% by only the IADPSG criteria. More than two-thirds who were identified by the IADPSG were not identified by WHO criteria, Dr. Morkrid pointed out.

After adjustment for ethnicity, age, BMI, body height, parity, education level, and first-degree relatives with diabetes, factors significantly associated with GDM by the WHO criteria were body height per cm (odds ratio, 0.92), low education level (OR, 1.83), and having a first degree relative with diabetes (OR, 2.28). With the IADPSG criteria, prepregnancy BMI (OR, 1.09) and South Asian origin (OR, 2.48) were the most significant factors.

In response to a question from the audience about fetal outcome, Dr. Morkrid responded that those data are available but have not yet been analyzed.

The IADPSG criteria have been adopted by some countries, including Japan and Germany, but not widely in the United States. In September 2010, the ACOG Committee on Obstetric Practice issued a committee opinion restating its recommendation for a “two-step” method that differs from both the IADPSG and WHO criteria, utilizing a 50-g, 1-hour “loading” test at 24-28 weeks' gestation, followed by a confirmatory 100-g, 3-hour OGTT.

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