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Weight Gain During Pregnancy: Reexamining the Guidelines

It has been nearly two decades since guidelines for how much weight a woman should gain during pregnancy were issued by the Institute of Medicine (IOM). In that time, more research has been conducted on the effects of weight gain in pregnancy on the health of both mother and baby. There have also been dramatic changes in the population of women having babies. American women are now a more diverse group; they are having more twin and triplet pregnancies, and they tend to be older when they become pregnant. Women today are also heavier; a greater percentage of them are entering pregnancy overweight or obese, and many are gaining too much weight during pregnancy. Many of these changes carry the added burden of chronic disease, which can put the mother and her baby's health at risk. Clearly, the time had come to reexamine the guidelines for weight gain during pregnancy issued in 1990 and to determine whether revision was needed to meet the needs of American women today. The Committee to Reexamine IOM Pregnancy Weight Guidelines undertook this challenge from the perspective that factors that affect pregnancy begin before conception and continue through the first year after delivery. One of the most important modifiers of pregnancy weight gain and its impact on a mother's and her baby's health is a woman's weight at the start of pregnancy. The best available measure of prepregnancy weight, body mass index (BMI, a measure of body fat based on weight and height), has been updated in the new guidelines to the categories developed by the World Health Organization (WHO) and adopted by the National Heart, Lung, and Blood Institute (NHLBI). In developing the new guidelines, the committee considered not only the welfare of the infant, as was done in 1990, but also the health of the mother. Thus, the new guidelines, shown in Table 1, differ from the previous ones in two important ways. First, they are based on the WHO BMI categories rather than the previous categories from the Metropolitan Life Insurance tables. Second, the new guidelines include a specific and relatively narrow range of recommended gain for obese women. Because positive outcomes are achieved within a range of weight gains, the new guidelines are formulated as a range of weight gain for each category of prepregnancy BMI. A single number cannot accommodate differences such as age, race/ethnicity, or other factors that may …