Proposed recommendations would increase number of women diagnosed with gestational diabetes

Two to three times more pregnant women may soon be diagnosed and treated for gestational diabetes, based on proposed measurements for determining blood glucose levels for the mother and unborn baby, according to a new study published in Diabetes Care.

The International Association of the Diabetes and Pregnancy Study Groups called for new criteria that require only a single measurement of fasting plasma glucose ≥92 mg/dL or a one-hour glucose tolerance test of ≥180 mg/dL or two-hour ≥153 mg/dL.

Using current guidelines, about 5% to 8% of pregnant women are diagnosed with gestational diabetes, according to Boyd Metzger, MD, chair of the group. However, the new guidelines would potentially identify more than 16% of the entire population of pregnant women as having gestational diabetes.

Although the newly recommended thresholds were previously considered to be within the safe, normal range, they are values at which there is increased risk for birth weight, cord C-peptide and body fat >90th percentile.

“At these levels, the frequency of having an overweight baby is almost double, the frequency of having pre-eclampsia is almost double and the frequency of early delivery is 40% greater,” Metzger said in a press release. “These are really substantial differences.”

The recommendations are the result of the deliberations by a consensus panel of more than 50 IADPSG delegates. The IADPSG panel reviewed several studies that examined associations of maternal glycemia with perinatal and long-term outcomes in offspring — particularly the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study, which evaluated more than 23,000 women enrolled during six years and concluded that even modest increases in maternal glucose increase the risk for adverse pregnancy outcomes.

“Our research represents an examination of risks and a consensus about how high a level the risk needs to reach before a diagnosis should be made and treatment should be considered,” Metzger said.

The group spent almost two years determining how to apply findings from the 2008 HAPO study, which was led by Metzger. Previous guidelines to diagnose gestational diabetes were based on blood glucose levels that identified women at high risk for developing diabetes in the future. The guidelines were not related to risks to the baby or other risks to the mother.

“Essentially, it is a paradigm shift for improved pregnancy outcome,” researcher Lois Jovanovic, MD, CEO and chief scientific officer of Sansum Diabetes Research Institute and clinical professor of medicine at University of Southern California-Los Angeles, told Endocrine Today.

“HAPO was an expensive study, and it took a long time to see the results, but it was worth waiting for. Now we need to implement it as quickly as possible,” said Jovanovic, also an Endocrine Today Editorial Board member.

According to supporters of the reclassification, the goal is to bring about a universal approach for diagnosis and classification of gestational diabetes.

“Now, we have an opportunity to have the whole world do one test, whereas previously, America did the two-step test while the rest of the world was moving toward the 75-g one step,” Jovanovic said.

The previous criteria for gestational diabetes diagnosis were established more than 40 years ago. In recent years, rates of gestational diabetes diagnoses have increased by as much as 50%, mirroring the obesity epidemic.

“We shouldn’t be surprised,” Metzger said. “The fact that we have a lot of gestational diabetes to deal with is consistent with the major impact that diabetes and obesity are having in our population at large. How could we expect pregnancy to escape that?”

Consensus concerns

In an accompanying editorial, Robert G. Moses, MD, of the South Eastern Sydney and Illawarra Area Health Service in Wollongong, New South Wales, Australia, said there are various concerns that accompany changes to gestational diabetes thresholds.

“The new criteria proposed would diagnose about 18% of all women in pregnancy as having gestational diabetes, which is about double the proportion of women hitherto designated. Clearly, the implications of this doubling will need serious considerations,” Moses wrote.

He said there are concerns related to “health care costs of these additional diagnoses as well as possible perceptions about the ‘medicalization’ of pregnancy,” adding that “the inevitable increase in costs may be a disincentive for some national health care systems to adopt a consensus approach.” – by Matthew Brannon

Metzger BE. Diabetes Care. 2010;33:676-682.

Moses RG. Diabetes Care. 2010;33:690-691.

The diagnostic criteria have been changing over the previous decades. For example, the FPG level for diagnosis moved from 140 mg/dL to 126 mg/dL since complications of diabetes were seen at lower glucose levels than the diagnostic levels. The HAPO trial seemed to confirm similar relationships in patients with gestational diabetes, in whom there was an apparent linear relationship between glucose levels and the classic complications. Furthermore, it seems appropriate to standardize testing both nationally and internationally - exactly what the American Diabetes Association recommends, to undertake future multicenter trials to confirm the advantages of interventions and to what level these interventions should aim for.

– Derek LeRoith, MD, PhD

Endocrine Today Editorial Board member