A Look at Two New Diabetes and Pregnancy Guidelines
Gestational diabetes, if caught early, can be managed without causing harm to the mother or infant. The two new guidelines differ on how and when to screen pregnant women.
Two medical organizations, The Endocrine Society and American Congress of Obstetricians and Gynecologists (ACOG), have slightly differing opinions on how to screen pregnant women for overt diabetes at the first prenatal visit and for gestational diabetes later during pregnancy, according to recently released guidelines from both associations.
Diabetic Lifestyle spoke with authors of both guidelines to discuss how physicians should interpret the guidelines in clinical practice.
Early Screening For Overt Diabetes: When and How?
The Endocrine Society guidelines recommend that all pregnant women should be screened for overt diabetes using blood glucose testing at their first prenatal visit, either before 13 weeks’ gestation or as soon as possible thereafter, as reported in the November issue of the Journal of Clinical Endocrinology and Metabolism. This recommendation is in alignment with that of the International Association of Diabetes and Pregnancy Study Groups and the American Diabetes Association.
The 2013 ACOG guidelines call for early screening for overt diabetes or gestational diabetes with blood glucose testing only in women identified as having risk factors for gestational diabetes (eg, a history of gestational diabetes, impaired glucose metabolism, or obesity). The ACOG guidelines were first published in the August issue of Obstetrics & Gynecology.
“There is insufficient data at the present time to endorse universal testing for diabetes at the first prenatal visit. It does, however, seem reasonable to test for diabetes in early pregnancy in women with obvious risk factors,” said co-author of the ACOG guidelines Mark B. Landon, MD, Chair and Professor in the Department of Obstetrics and Gynecology at Ohio State University, Columbus, Ohio. “The issue has not been adequately studied in any large population to assess harms, benefits, costs, and other associated considerations,” he said.
While these screening recommendations appear to differ, “there is actually great similarity between what ACOG and what we are recommending, it is just a matter of how we screen,” said Ian Blumer, MD, of the Charles H. Best Diabetes Centre in Whitby, Ontario, Canada, and chair of the task force that authored The Endocrine Society guidelines.
While The Endocrine Society recommends using blood glucose testing directly for early screening for overt diabetes in all women, ACOG uses a clinical screen initially followed by blood work in women with diabetes risk factors. Because so many women have risk factors for diabetes and, thus, would require screening using blood work under both guidelines, Dr. Blumer believes that the recommendations are actually “very much in alignment.”
“Because untreated diabetes can harm both the pregnant woman and the fetus, it is important that testing for diabetes be done early on in pregnancy so that if diabetes is found appropriate steps can be immediately undertaken to keep both the woman and her fetus healthy,” said Dr. Blumer.
Are Lower Glucose Level Cutoffs Appropriate When Screening for Gestational Diabetes?
The Endocrine Society recommends using the IADPSG 1-step approach to diagnose gestational diabetes: a 2-hr, 75-g oral glucose tolerance test (OGTT) that is given to all pregnant women between week 24-28 gestation. Only 1 of the following 3 threshold values needs to be met or exceeded to diagnose gestational diabetes using these guidelines: fasting plasma glucose level >92 mg/dL; 1-hour value ≥180 mg/dL; and 2-hour value ≥153 mg/dL.
In contrast, ACOG recommends a 2-step approach that involves an initial 1-hr, 50-g screening test and, for women who met or exceeded a threshold of 135 or 140 mg/dL, a 3-hour diagnostic OGTT using a 100-g load, Dr. Landon explained. For the 3-hour OGTT, two or more of the threshold values (ie, either the Carpenter and Coustan criteria or the plasma levels established by the National Diabetes Data Group) must be met to diagnose gestational diabetes.
“The IADPSG criteria, which are endorsed by The Endocrine Society, could identify as many as 18% of the United States population as having gestational diabetes, which represents at a minimum a two- if not three-fold increase in the frequency of this condition compared to using the 2-step, 3-hr OGTT approach,” commented Dr. Landon. “While there are two large-scale randomized clinical trials that show a benefit to treating mild gestational diabetes, both of these studies utilize criteria that is different than the proposed IADPSG cutoffs,” he noted. In fact, one of the studies conducted by the NICHD and led by Dr. Landon used the Carpenter and Coustan criteria for diagnosis, which is one of the two criteria supported by ACOG, he added.
The Endocrine Society would rather cast a wide net to make sure that the great majority of women with gestational diabetes are detected and treated, recognizing that some women may be diagnosed with gestational diabetes who otherwise would have had health pregnancies, Dr. Blumer said. Until a definitive randomized outcome study is conducted to determine the best strategy for screening and diagnosis, “we have to use both the best available data and our best clinical judgment,” he said.
“The fact that we recommend a single step process for diagnosis with a lower criteria (as do the IADPSG and ADA), and ACOG recommends a more traditional approach is reflective of the fact that there is uncertainty here,” Dr. Blumer said. “In science there is always going to be some uncertainty,” he added.
Dr. Blumer emphasized that The Endocrine Society guideline is “not just a gestational diabetes guideline, but, rather is a much more encompassing guideline discussing everything from preconception care all the way to the postpartum period.” He adds that “Most people so far are just focusing on the screening recommendations we make for overt diabetes in early pregnancy and those for gestational diabetes later in pregnancy, but it is a much broader document. I hope readers will find value in the entirety of it, not just the controversial parts.”