A R T I C L E
Gestational Diabetes Mellitus
Tracy L. Setji, MD; Ann J. Brown, MD; and Mark N. Feinglos, MD, CM
estational diabetes mellitus (GDM) is defined as glucose intolerance that begins or is first detected during pregnancy.1–3 GDM affects ~ 7% of all pregnancies, resulting in > 200,000 cases per year.2 Depending on the population sample and diagnostic criteria,the prevalence may range from 1 to 14%.1,2 Of all pregnancies complicated by diabetes, GDM accounts for ~ 90%.1
Table 1. ADA and WHO Criteria for the Diagnosis of GDM2,6 ADA 100-g OGTT 95 180 155 140 ADA 75-g OGTT 95 180 155 — WHO 75-g OGTT 126 — 140 —
Fasting (mg/dl) 1-hour (mg/dl) 2-hour (mg/dl) 3-hour (mg/dl)
For the ADA criteria, two or more of the values from either the 100- or 75-gOGTT must be met or exceeded to make the diagnosis of GDM. For the WHO criteria, one of the two values from the 75-g OGTT must be met or exceeded to make the diagnosis of GDM.
DIAGNOSTIC CRITERIA The oral glucose tolerance test (OGTT) most commonly used to diagnose GDM in the United States is the 3-hour, 100-g OGTT. According to diagnostic criteria recommended by the American DiabetesAssociation (ADA), GDM is diagnosed if two or more plasma glucose levels meet or exceed the following thresholds: fasting glucose concentration of 95 mg/dl, 1-hour glucose concentration of 180 mg/dl, 2-hour glucose concentration of 155 mg/dl, or 3-hour glucose concentration of 140 mg/dl.1,2,4 These values are lower than the thresholds recommended by the National Diabetes Data Group and are based on theCarpenter and Coustan modification.5 The ADA recommendations also include the use of a 2-hour 75-g OGTT with the same glucose thresholds listed for fasting, 1-hour, and 2-hour values.1,2 The World Health Organization (WHO) diagnostic criteria, which are used in many countries outside of North America, are based on a 2-hour 75-g OGTT. GDM is diagnosed by WHO criteria if either the fasting glucose is> 126 mg/dl or the 2-hour glucose is > 140 mg/dl. Table 1 summa-
rizes ADA and WHO criteria for the diagnosis of GDM. The Brazilian Gestational Diabetes Study evaluated the ADA and WHO diagnostic criteria against pregnancy outcomes in an observational cohort study of nearly 5,000 women. Using the 2-hour 75-g OGTT criteria proposed by the ADA, the incidence of GDM was 2.4% (95% CI 2.0–2.9). Theincidence of GDM using the WHO criteria was 7.2% (6.5–7.9). Both the ADA and WHO criteria predicted an increased risk of macrosomia, preeclampsia, and perinatal death. However, this increase was not statistically significant for macrosoIN BRIEF
mia by the ADA criteria or for perinatal death by the WHO criteria. This study concluded that, although the WHO criteria identified more cases of GDM,both the ADA and WHO criteria are valid options for the diagnosis of GDM and the prediction of adverse pregnancy outcomes.6 PATHOGENESIS Pregnancy is a diabetogenic condition characterized by insulin resistance with a compensatory increase in -cell response and hyperinsulinemia. Insulin resistance usually begins in the second trimester and progresses throughout the remainder of the pregnancy.Insulin sensitivity is reduced by as much as 80%. Placental secretion of hormones, such as progesterone, cortisol, placental lactogen, prolactin, and growth hormone, is a major contributor to the insulin-resistant state seen in pregnancy. The insulin resistance likely plays a role in ensuring that the fetus has an adequate supply of glucose by changing the maternal energy metabolism from carbohydratesto lipids.7 Women with GDM have a greater severity of insulin resistance compared
Gestational diabetes mellitus (GDM) is a common condition affecting ~ 7% of all pregnancies. The detection of GDM is important because of its associated maternal and fetal complications. Treatment with medical nutrition therapy, close monitoring of glucose levels, and insulin therapy if glucose levels are above...