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According to the Centers for Disease Control and Prevention (2020), nearly 27 million adults in the United States have been diagnosed with diabetes. Another 7.3 million are suspected to be undiagnosed, and an estimated 88 million have prediabetes. Reasons for these substantial rates include an aging population, which is more likely to develop type 2 diabetes; population growth within minority groups at particular risk for type 2 diabetes; and a dramatic rise in obesity rates. In 2019, almost three in 10 women were considered obese prior to becoming pregnant (Driscoll, 2020). The strong relationship between diabetes and the current obesity epidemic in the United States underlines the critical need for diet and lifestyle interventions to change the trajectory of both.


In nonpregnant individuals, the type of diabetes is based on its presumed pathogenesis and its manifestations. Absolute insulin deficiency, which generally is autoimmune in etiology, characterizes type 1 diabetes. In contrast, insulin resistance, relative insulin deficiency, or elevated glucose production characterizes type 2 diabetes (Table 60-1). Both types are generally preceded by a period of abnormal glucose homeostasis often referred to as prediabetes. Pancreatic β-cell destruction can begin at any age, but type 1 diabetes is clinically apparent most often before age 30. Type 2 diabetes usually develops with advancing age but is increasingly identified in younger obese adolescents. Etiological overlap in diabetes subtypes is well established and has led to the proposal of a single classification system centered on β-cell function along with the concept of individualized treatment strategies (World Health Organization, 2020). Other forms of diabetes include maturity-onset diabetes of the young (MODY). The more common MODY type is in obese adolescents (TODAY Study Group, 2021). The less common form is an autosomal dominant condition and characterized by mild diabetes diagnosed in adolescence or young adulthood (Udler, 2020).

TABLE 60-1Etiological Classification of Diabetes Mellitus

Classification During Pregnancy

Diabetes is the most common medical complication of pregnancy. Women can be separated into those diagnosed with diabetes before pregnancy—pregestational or overt diabetes, and those diagnosed during pregnancy—gestational diabetes.

The proportion of pregnancies complicated by ...

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