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Glucose Tolerance in Gestational Diabetes May Predict Later Diabetes

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Glucose Tolerance in Gestational Diabetes May Predict Later Diabetes

Gestational diabetes can be frightening to women who develop it, for several reasons. It means having to check and manage blood glucose levels for the first time, on top of all the other practical aspects of managing a pregnancy. It means potentially worrying about pregnancy outcomes related to having gestational diabetes. And because it’s associated with a higher risk of developing diabetes later on in life, it means managing your future diabetes risk even after your pregnancy.

But it’s difficult to predict which women with gestational diabetes will develop diabetes later on, beyond usual risk factors like body weight and family history of diabetes. So in a recent analysis, researchers looked at whether two common tests used to assess glucose tolerance, when taken during a pregnancy with gestational diabetes, could predict a woman’s future diabetes risk.

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Assessing future diabetes risk

In an article published in the Journal of Diabetes and its Complications, researchers reviewed studies on gestational diabetes and future diabetes risk that were published between 1982 and 2020. The researchers were interested in whether this risk was higher or lower based on participants’ measurements from an oral glucose tolerance test (OGTT) taken before they gave birth.

After extracting data on OGTT values during pregnancy and diabetes diagnoses after pregnancy, the researchers found that both OGTT results and measured fasting blood glucose levels were associated with the risk of a later diabetes diagnosis during the average follow-up period of just over seven years. Women with elevated fasting blood glucose were 3.62 times as likely to develop diabetes later on, while those with an OGTT result above the normal range were 3.96 times as likely to develop diabetes during the follow-up period.

But these somewhat clear results were made muddier once the researchers controlled for certain characteristics of the participants that could affect future diabetes risk, such as body-mass index (BMI, a measure of body weight that takes height into account), age at the time of giving birth, and whether they had a family history of diabetes. After adjusting for these and other factors, OGTT results and fasting blood glucose were much weaker predictors of future diabetes risk. Women with elevated fasting glucose were only 1.58 to 1.91 times as likely to develop diabetes in the future, and those with an OGTT result above the normal range were 1.95 times as likely to develop diabetes in the future.

Based on the size of the study groups, these adjusted results mean that fasting blood glucose levels didn’t significantly predict future diabetes risk in most studies, while OGTT results weren’t at all significantly associated with future diabetes risk.

Not significant, but still important?

Despite the researchers’ findings that fasting blood glucose and OGTT results weren’t independent, significant predictors of future diabetes risk in nearly all cases, that doesn’t mean these measurements don’t mater in a real-world setting.

In fact, the unadjusted results — showing a clear relationship between these numbers and future diabetes risk — may be more important for women and their doctors when it comes to looking out for future diabetes risk. Even if these numbers reflect risks for diabetes due to factors like body weight or age, they can still accurately be tied to the likelihood of developing diabetes in the future — more so than the “adjusted” numbers by themselves. In the real world, it’s more important to identify who is at risk for diabetes in the future — something the unadjusted numbers do — than to rule out other factors that may account for this risk.

So if you develop gestational diabetes and have an out-of-range fasting glucose level or OGTT result during your pregnancy, it’s especially important to get screened regularly for diabetes after your pregnancy, and to take recommended steps — including lifestyle measures — to reduce your future diabetes risk.

Want to learn more about treatment for gestational diabetes? Read “Gestational Diabetes: Once You’re Diagnosed,” “Gestational Diabetes: More Treatment Approaches” and “Glucose Test During Pregnancy for Gestational Diabetes.”

Quinn Phillips

Quinn Phillips

Quinn Phillips on social media

A freelance health writer and editor based in Wisconsin, Phillips has a degree from Harvard University. He is a former Editorial Assistant for Diabetes Self-Management and has years of experience covering diabetes and related health conditions. Phillips writes on a variety of topics, but is especially interested in the intersection of health and public policy.

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