Abstract and Introduction
Obesity and unintended pregnancy differentially affect women based on sociodemographic factors. Because of the overlap of these factors, obesity and unintended pregnancy have been described as colliding epidemics. Understanding the relationship between obesity and unintended pregnancy, contraceptive use, and sexual behavior is important in improving the reproductive health of women given the increasing weight demographic. A review of the literature reveals contraceptive use versus nonuse does not differ in women of different body weights. Obese women use oral contraceptives less than normal weight women and are more likely to use procedural methods like sterilization. No difference was noted in most types of sexual behavior for women of different body weights.
Unintended pregnancy and obesity have been described as colliding overlapping epidemics. In 2008, 28.6% of adult women in the United States were overweight; 35.5% were obese. Rates of unintended pregnancy are even more staggering. Half of all pregnancies in the United States are unintended, resulting in >3.2 million unintended pregnancies and 1.2 million abortions in the United States every year.[2,3] Despite the development of multiple forms of effective contraception, these rates have not changed substantially in the last decade.
Body mass index (BMI), defined as weight in kilograms divided by height in meters squared, is the standard measure used to assess obesity. BMI is closely correlated with body fat and the health-related consequences of obesity. However, it is not a perfect measure and overestimates body fat in very muscular individuals and underestimates body fat in the elderly who have less muscle mass. The World Health Organization and the National Institutes of Health defines overweight as a BMI between 25 kg/m2 and 30 kg/m2 and obesity as a BMI of ≥30 kg/m2.[4,5] These BMI cut-off points are based on epidemiological studies done primarily in white populations. Increasing evidence indicates the levels of health-related risk associated with BMI vary across racial groups. In particular, Asians are noted to be at risk for developing weight-related morbidity such as diabetes and dyslipidemia at BMIs <30 kg/m.[2,7,8]
The most accurate estimates of the prevalence of obesity come from the National Health and Nutrition Examination Survey (NHANES) in which height and weight were measured rather than self-reported. Between 1960 and 1980, women had a 15 to 17% prevalence of obesity, which was higher than the 10 to 12% reported in men. In the 1980s, the prevalence of obesity in both men and women began to increase markedly ([Fig. 1]). Data from 1988 to 1994 show the prevalence of obesity to be 26.0% in women and 20.6% in men. The most recent NHANES database indicates prevalence continues to increase, although not as dramatically as it did in the 1980s and 1990s.
Trends in the prevalence of overweight and obesity in women in the United States. Data from National Health Examination Survey (1960–1962) and the National Health and Nutrition Examination Survey (1971 to 2008).
Higher rates of both obesity and unintended pregnancy are associated with lower income and racial and ethnic minority status.[1,3] For example, the poorest counties in the United States have the highest rates of obesity. Women with a household income <100% of the poverty level have an unintended pregnancy rate five times higher than women with an income >200% of the poverty level. Approximately 30% of non-Hispanic white adults are obese compared with 45% of non-Hispanic blacks and 36.8% of Hispanic adults. The unintended pregnancy rate varies from 36 per 1000 non-Hispanic white women to 91 per 1000 non-Hispanic black women and 82 per 1000 Hispanic women.
In this article, we discuss two important factors that contribute to unintended pregnancy: contraceptive use and sexual behavior. Much of the information on this topic comes from the analysis of large nationally representative surveys like the National Survey of Family Growth, Behavioral Risk Factor Surveillance System (BRFSS), and the Pregnancy Risk Assessment Monitoring System (PRAMS) ( Table 1 ). Because these databases are cross sectional, described relationships consist of associations and cannot be deemed causal. Also, heights and weights in most of these surveys were self-reported rather than objectively measured. This is a reasonable way to estimate BMI, although it is not as accurate as objectively measuring height and weight.[13,14] Although many surveys used a computer-assisted personal interviewing system in which the respondent answered questions confidentially, outcomes like sexual activity, unintended pregnancy, and abortion are known to be underreported, which should be considered in interpreting the results of these studies.[15,16]
Semin Reprod Med. 2012;30(6):459-464. © 2012 Thieme Medical Publishers