A 1-hour glucose measure may better predict postpartum diabetes risk than 2-hour glucose
Key takeaways:
- Researchers identified more women with dysglycemia using 1-hour vs. 2-hour glucose values.
- One-hour glucose at 3 months postpartum was the strongest predictor for future dysglycemia risk.
The use of a 1-hour oral glucose tolerance test instead of a 2-hour OGTT may be more accurate in detecting diabetes postpartum, especially among women who had gestational diabetes during pregnancy, according to study findings.
Women often do not return to undergo a postpartum 2-hour OGTT in part due to the time commitment the test requires, according to Ravi Retnakaran, MD, MSc, FRCPC, professor of medicine at the University of Toronto and an endocrinologist at the Leadership Sinai Centre for Diabetes at Mount Sinai Hospital in Toronto. Women with gestational diabetes during pregnancy are at increased risk for developing type 2 diabetes postpartum and missing an OGTT could lead to a delayed diagnosis, he said.
In 2024, the International Diabetes Federation published a position statement in Diabetes Research and Clinical Practice endorsing the use of a 1-hour OGTT for the diagnosis of intermediate hyperglycemia and type 2 diabetes. In a study published in Diabetes Care, Retnakaran and colleagues compared 1-hour glucose values on an OGTT with 2-hour glucose values for the detection of postpartum dysglycemia among women with gestational diabetes during pregnancy.
“There’s been a developing literature around the idea that you could do an OGTT with a 1-hour test rather than a 2-hour test,” Retnakaran told Healio. “The postpartum 2-hour OGTT that is recommended in women with a history of gestational diabetes is the most frequent setting outside of pregnancy in which an OGTT is the recommended test. ... We felt this is the very [population] where you need to test the 1-hour test vs. the 2-hour test.”
Using 1-hour glucose as a predictor
Researchers conducted a prospective observational study of 369 women who underwent a multi-sample 2-hour OGTT at 3 months, 1 year, 3 years and 5 years postpartum. Dysglycemia was defined as a composite of intermediate hyperglycemia, prediabetes or diabetes as defined by either the International Diabetes Federation’s 1-hour OGTT criteria or WHO’s 2-hour OGTT criteria.
When participants were divided into tertiles based on 1-hour glucose value, women in the highest tertile had lower whole-body insulin sensitivity (P < .0001) and worse beta-cell function (P < .0001) than those in the lowest tertile. Similar trends were observed with fasting glucose and 2-hour glucose values.
At 3 months, 1-hour glucose identified dysglycemia in 60 of 70 women who had dysglycemia using 2-hour glucose measures. Using a 1-hour glucose value also identified dysglycemia in an additional 96 women who did not have dysglycemia on their 2-hour glucose value. At 1 year, 3 years and 5 years, more women were diagnosed with dysglycemia using 1-hour glucose vs. 2-hour glucose.
In adjusted analyses, 1-hour glucose at 3 months was the strongest predictor for assessing future dysglycemia over the first 5 years postpartum, followed by 2-hour glucose, “non-white” ethnicity, fasting glucose and BMI. The findings were similar in subanalyses limited to women with normal glucose tolerance at 3 months and women who were recently diagnosed with gestational diabetes.
“The findings for the 1-hour glucose value in this study fit very well with the larger literature around the 1-hour test vs. the 2-hour test,” Retnakaran told Healio. “What we’ve done is apply it to the specific clinical setting where it may be most important at this point in time.”
Clinical trial planned
Retnakaran said his team is planning to conduct a clinical trial that would randomly assign pregnant women to undergo 1-hour OGTT or 2-hour OGTT postpartum. He added the trial will go beyond just examining future diabetes risk and look at overall future cardiometabolic risk.
If the findings of the observational study are confirmed in the trial, it could lead to a change in practice toward using a 1-hour OGTT for postpartum reclassification in women with gestational diabetes, according to Retnakaran.
“We are at a remarkable point in time currently, where you have interventions that potentially may be able to modify diabetes risk or decrease it,” Retnakaran said. “Specifically ... the capacity for weight loss, because we know that in individuals who are at risk for diabetes, the capacity to achieve weight loss can reduce their risk of progressing to diabetes. If you don't detect such women at this point in time — the women who are at risk on the basis of having hyperglycemia in pregnancy — there is a greater opportunity cost now than ever before.”
Reference:
For more information:
Ravi Retnakaran, MD, MSc, FRCPC, can be reached at ravi.retnakaran@sinaihealth.ca.
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