Universal Diabetes Testing Recommended at First Prenatal Visit

Troy Brown, RN

November 07, 2013

All pregnant women should be tested for diabetes at their first prenatal visit, unless they have already been diagnosed with the condition, according to a new clinical practice guideline from the Endocrine Society.

"Until very recently, anybody who had elevated blood glucose above a certain threshold discovered during pregnancy by definition had to be labeled as gestational diabetes until they delivered… There are lots of women who had preexisting diabetes, but nobody knew it," explained task-force chair Ian Blumer, MD, a diabetes specialist, medical advisor, and board member of the Charles H. Best Diabetes Centre and a professor at the University of Toronto, Ontario.

"[It's] not just a gestational-diabetes guideline — it's a guideline on all aspects of diabetes and pregnancy," he noted.

This new guidance is important because cases of diabetes are being missed in pregnant women by traditional screening methods, said Dr. Blumer. For example, while as many as 1 in 5 pregnant women develops gestational diabetes, conventional testing identifies only about a quarter of these cases, which means that many women go undiagnosed and are therefore at increased risk for pregnancy complications.

Of interest, the Endocrine Society is leaning toward a technically 1-step approach for the testing of gestational diabetes, in line with the American Diabetes Association (ADA) but in contrast to the American College of Obstetricians and Gynecologists (ACOG) and the National Institutes of Health. This 1-step approach uses a lower level of blood glucose to diagnose gestational diabetes and is a subject of contention, with critics saying that it will increase the frequency of diagnosis of gestational diabetes 2- to 3-fold.

Dr. Blumer and colleagues publish the clinical practice guideline in the November 2013 issue of the Journal of Clinical Endocrinology and Metabolism .

Guidelines More Precise on Who Can Be Diagnosed With Overt Diabetes

The new clinical practice guideline recommends universal testing for diabetes with a fasting plasma glucose (FPG) test, HbA1c, or an untimed random plasma glucose at the first prenatal visit (prior to 13 weeks' gestation or as soon as possible thereafter) for women who have not already been diagnosed with diabetes.

Those with FPG of 126 mg/dL or higher (>7.0 mmol/L), untimed random plasma glucose 200 mg/dL or higher (>11.1 mmol/L), or HbA1c 6.5% or higher would be deemed to have overt diabetes (type 1, type 2, or other), as opposed to FPG of 92 to 125 mg/dL (5.1–6.9 mmol/L), which would be classified as gestational diabetes.

For those with overt diabetes, the diagnosis must be confirmed by a second test (an FPG, untimed random plasma glucose, HbA1c, or oral glucose tolerance test [OGTT]), which must be done in the absence of hyperglycemia symptoms and be abnormal on another day.

"[The guideline is] more precise in terms of who we can comfortably diagnose [with] overt diabetes vs gestational diabetes," Dr. Blumer explained.

Gestational Diabetes Testing at 24 to 28 Weeks' Gestation, Technically 1 Step

Pregnant women not already diagnosed with overt or gestational diabetes by 24 weeks should be tested for gestational diabetes with a 2-hour, 75-g OGTT between 24 to 28 weeks' gestation, using the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria, the guidance states.

"Our recommendation…in agreement with the recommendations of the IADPSG and ADA, differs materially from the recommendation of other organizations, including the American College of Obstetricians and Gynecologists and the National Institutes of Health," the authors write in the guideline.

The Endocrine Society advice doesn't fit neatly into a "1-step" or "2-step" approach, however, Dr. Blumer noted. "In one sense, we are advocating — as is the ADA — for the 1-step approach, where at 24 to 28 weeks people have a glucose tolerance test without a preceding 50-g challenge… The only modification is we tried to clarify the diagnosis of type 2 diabetes during pregnancy, [so]…we're also advocating for testing at the first antenatal visit."

In contrast, "The American College of Obstetricians and Gynecologists…recommends that, in terms of screening for gestational diabetes, the traditional approach of a 50-g challenge and then a 3-hour 100-g glucose tolerance test be performed, and their cutoff points for diagnosis were the same as those that have been classically used," he noted.

For testing for gestational diabetes, the 75-g OGTT should be performed after fasting overnight for at least 8 hours (but not more than 14 hours) and not reducing usual carbohydrate intake for the preceding several days.

The new clinical practice guideline states that gestational diabetes is diagnosed if a 2-hour 75-g OGTT value at 24 to 28 weeks is 153 to 199 mg/dL (8.5–11.0 mmol/L). If the OGTT at 2 hours is 200 mg/dL or higher (>11.1 mmol/L), this constitutes overt diabetes.

Test Women With Gestational Diabetes After Birth to Rule Out Overt Diabetes

Other important recommendations noted by the Endocrine Society in the clinical practice guideline include recommending weight loss prior to pregnancy for women with diabetes who are overweight or obese.

If gestational diabetes is diagnosed, it recommends initial treatment should be lifestyle oriented (ie, medical nutrition therapy and daily moderate exercise lasting at least 30 minutes). If lifestyle therapy is insufficient to control blood glucose, the next step is pharmacological treatment, and it provides advice on the available therapeutic options.

And for women with gestational diabetes, an OGTT should be performed 6 to 8 weeks after delivery to rule out diabetes or prediabetes, it stresses. Such women should also be tested regularly for diabetes, particularly before becoming pregnant again, it notes.

Women With Diabetic Retinopathy Should Be Treated Before Conceiving

The clinical practice guideline also recommends that women with type 1 or type 2 diabetes should undergo a detailed eye exam to check for diabetic retinopathy, and if damage to the retina is found, they should have treatment before conceiving.

Dr. Blumer reports financial or business/organizational interest in AstraZeneca, Bayer, Bristol-Myers Squibb, Eli Lilly, GlaxoSmithKline, Janssen Pharmaceuticals, Medtronic, Novo Nordisk, Roche, Sanofi, and Takeda. Disclosures for the coauthors are listed in the article.

J Clin Endocrinol Metab. 2013;98:4227-4249. Abstract

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