Obesity is a complex and multifactorial metabolic heterogeneous disorder that chronically affects the individual. The World Health Organization (WHO) characterizes obesity as a pandemic health issue with a higher prevalence in females than males. In the United States, more than 33% of women are obese.1 Obesity is the second leading cause of preventable deaths. While the complete pathogenesis of obesity is only partly understood, its effects on health are far reaching, with the aggregate cost of obesity in the United States ranging from 5% to 7% of annual medical expenditures.2 Obesity is defined as 35% or greater total body fat in women.3
In 1832, Quetelet proposed an index to characterize human health status (Table 20-1).4 Keys reaffirmed the validity of this index in 1972 by introducing the concept of the body mass index (BMI) and recommending it as a proxy for measuring body fat.5 WHO and the National Institutes of Health (NIH) in the United States classify obesity utilizing BMI. This marker is defined as the individual’s body weight divided by the square of his or her height, or BMI = W/H2, and is reported as kilograms per square meter (kg/m2) (Table 20-1). BMI values are age independent and are used for both sexes. Maternal ethnicity is under scrutiny to determine its association with BMI.
TABLE 20-1Definitions of Obesitya ||Download (.pdf) TABLE 20-1 Definitions of Obesitya
The Quételet index (homme moyen), 1832; then Keys’s 1972 body mass index
World Health Organization/National Institutes of Health: Body mass index
Body Mass Index (BMI) = W/H2 or kg/m2
| ||BMI |
|Recommended weight ||18.5–24.9 |
|Overweight ||25.0–29.9 |
|Obesity ||≥30 |
|Class I ||30–34.9 |
|Class II ||35–39.9 |
|Class III (morbid obesity) ||≥40 |
|With comorbidities ||≥35 |
|Super- (extreme) obesity (2.9%) ||≥35 |
|aEknoyan G. The average man and indices of obesity. Adolphe Quetelet (1796–1874). Nephrol Dial Transplant. 2008;1:47–51. |
IMPACT OF OBESITY ON PREGNANCY
Obesity represents increasingly serious maternal and perinatal health concerns when associated with a woman’s pregnancy. In 1988, Thomson and Hanley stated that short maternal stature and increased BMI predisposed patients to difficult labor. WHO estimated that 60% of women between the ages of 20 and 40 years are overweight or obese, as classified by their BMI. In the United States, more than 50% of pregnant women are overweight or obese, and 8% of reproductive-age women are extremely obese, with a BMI greater than 50 kg/m2, a group that is rapidly increasing,1 as reaffirmed by the National Health and Nutrition Examination Survey (NHANES).
Women suffering from obesity are at an increased risk for delayed conception.6 In the preconception period, obstetricians have an opportunity to counsel obese women. Timing of these efforts is critical to ...