NEW YORK – The incidence of gestational diabetes will rise substantially now that the American Diabetes Association has formally adopted new diagnostic criteria, especially in selected regions where pregnant woman may be older or have a higher prevalence of obesity.
Among the 15 geographically diverse communities that participated in the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study, the results of which led to the new ADA guidelines, the incidence of gestational diabetes ran as high as 24%, in Cleveland, while also reaching a low of 9%, in two communities in Israel.
The overall gestational diabetes incidence rate in HAPO averaged 16%, Dr. Boyd E. Metzger said at the meeting, sponsored by the American Diabetes Association, strikingly above the 7% rate documented as recently as 2005 in a large group of women from southern California (Diabetes Care 2008;31:899-904). But Dr. Metzger also expressed optimism that most of the added new cases of gestational diabetes that the new criteria identify will respond to lifestyle management, and that the net result of broader diagnosis and treatment will be a substantially reduced rate of adverse sequelae.
“The mild gestational diabetes that makes up the expanded population should be patients we can successfully manage with less expensive” lifestyle treatment, said Dr. Metzger, a professor of nutrition and metabolism at Northwestern University in Chicago. The increased numbers may also include “a modest increase in those who need drug treatment.” In general, “a more aggressive approach to diagnosis and treatment should lead to a reduction in complications of gestational diabetes. It would be disappointing if we can't achieve in the real world what the research study showed,” he said in an interview.
The new gestational diabetes diagnostic criteria received formal adoption from the American Diabetes Association in the group's annual position statement on Standards of Medical Care in Diabetes, published in January (Diabetes Care 2011;34:S11-61). The Standards' section on the detection and diagnosis of gestational diabetes cited the 2008 HAPO study (N. Engl. J. Med. 2008;358:1991-2002) as the basis for the new diagnostic criteria.
An initial proposal of the new criteria came from the International Association of Diabetes and Pregnancy Study Groups Consensus Panel last year, which recommended criteria to identify a woman with gestational diabetes if at week 24-28 her fasting plasma glucose was at least 92 mg/dL, or her plasma glucose 1 hour after an oral glucose challenge was at least 180 mg/dL, or her plasma glucose 2 hours after the glucose challenge was at least 153 mg/dL.
The new criteria “are not very different from the old ADA criteria. The biggest single difference is that any one of these criteria diagnoses an abnormal glucose level rather than requiring woman to meet at least two of the criteria,” said Dr. Metzger, lead author for both HAPO and for the IADPSG. This easing to allow diagnosis based on just one criterion “accounts for a lot of the increase in numbers,” he said. In the HAPO findings from more than 23,000 women, the fasting plasma glucose criterion diagnosed 8.3% of the women as having gestational diabetes, the 1-hour postchallenge plasma glucose level identified an additional 5.7% of women with gestational diabetes, and the 2-hour post-challenge glucose level identified another 2.1% with gestational diabetes, together totaling just over 16% with the diagnosis.
Data documenting the broad range of geographic variation in gestational diabetes incidence appeared in a report presented by a group of HAPO investigators, including Dr. Metzger, last September at the annual meeting of the European Association for the Study of Diabetes in Stockholm.
According to that report, 5 of the 15 HAPO sites had rates of 21%-24%, led by Cleveland with the highest rate and followed by Bellflower, Calif.; Singapore; Bangkok; and Manchester, England. Two different communities contributing data in Israel both had 9% rates, with the remaining eight sites having gestational diabetes rates of 10%-17%.
Having new diagnostic criteria also raises the question of whether treatment goals will need changing, said Dr. Metzger.
“We would like to get women [diagnosed with gestational diabetes] to a fasting plasma glucose of 90 mg/dL or below. When the diagnostic threshold is 92 mg/dL, if we don't get them to below then we are not changing their risk,” he said. But “we are not proponents of oral agents” for treating gestational diabetes.
“I don't have a lot of experience using the new criteria,” he admitted. “We just introduced them [at Northwestern University Medical Center] in January,” after their official endorsement from the ADA, Dr. Metzger said.
“We don't yet have the data to make new treatment recommendations. The right treatment targets will need to be defined by results from additional studies.”