Excessive weight has become one of the major health problems in affluent societies. Because of its medical importance and its multifaceted effects on pregnancy, it is discussed separately in this chapter. The prevalence of obesity in the United States has increased steadily as economic prosperity has increased. For a number of years, obesity has been termed epidemic—strictly defined, this implies a temporary widespread outbreak of greatly increased frequency and severity. Unfortunately, obesity more correctly is endemic—a condition that is habitually present. Moreover, its prevalence has continued to increase since 1960. By 1991, approximately a third of adults in the United States were overweight, and almost 300,000 deaths were attributed annually to obesity (Allison and co-workers, 1999). Sadly, the problem is not limited to adults, and 15 percent of children aged 6 through 11 years are reported to be overweight (Ogden and associates, 2002). The prevalence in adolescents is similar.


Public health authorities began to address the problem of obesity in the late 1980s. A stated goal of Healthy People 2000 was to reduce the prevalence of overweight people to 20 percent or less by the end of the 20th century (Public Health Service, 1990). Not only was this goal not achieved, but by 2000, more than half of the population was overweight, and nearly a third of adults were obese (Flegal and colleagues, 2002; Hedley and associates, 2004).


There are many obesity-related diseases, including diabetes, heart disease, hypertension, stroke, and osteoarthritis. Together they result in a decreased life span. The worldwide diabetes epidemic that Bray (2003) predicted would follow the worldwide obesity epidemic has already begun. Obese women who become pregnant—and their fetuses—are predisposed to a variety of serious pregnancy-related complications. Long-term maternal effects include significant and increased rates of morbidity and mortality. Moreover, recent studies show that the offspring of obese women also suffer long-term morbidity.


A number of systems have been used to define and classify obesity. The body mass index (BMI), also known as the Quetelet index, is currently in use. The BMI is calculated as weight in kilograms divided by height in square meters (kg/m2). Calculated BMI values are available in various chart and graphic forms, such as the one shown in Figure 43-1. According to the National Heart, Lung, and Blood Institute (1998), a normal BMI is 18.5 to 24.9 kg/m2; overweight is a BMI of 25 to 29.9 kg/m2; and obesity is a BMI of 30 kg/m2 or greater. According to Freedman and colleagues (2002), obesity is further categorized as class I (BMI: 30 to 34.9 kg/m2), class II (BMI: 35 to 39.9 kg/m2), and class III (BMI: 40-plus kg/m2).

Figure 43-1
Graphic Jump Location

Chart for estimating body mass ...

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