Implementation of the New Institute of Medicine Gestational Weight Gain Guidelines

Anna Maria Siega-Riz, PhD, RD; Andrea Deierlein, PhD, MPH; Alison Stuebe, MD, MSc

Disclosures

J Midwifery Womens Health. 2010;55(6):512-519. 

In This Article

What are the New Gestational Weight Gain Guidelines?

The 2009 IOM gestational weight gain recommendations, including total weight gains and trimester-specific rates of weight gain, are shown in Table 1. Similar to the 1990 recommendations, they are specific for maternal prepregnancy BMI categories; however, there are several key revisions incorporated into the new recommendations:

Prepregnancy Body Mass Index Categories

In the new guidelines, the BMI cut-points for weight categories have changed from the Metropolitan Life Insurance Table values of 19.8, 26, and 29 to the more commonly used International Obesity Task Force (IOTF) values of 18.5, 25, and 30. Using these values, women are categorized as underweight (<18.5), normal weight (18.5–24.9), overweight (25.0–29.9), or obese (≥30). The main implication of this change is that a smaller proportion of women will be classified as underweight before pregnancy while a larger proportion will be classified as overweight. Adoption of the IOTF BMI categories, which were developed more recently and are now implemented worldwide by the World Health Organization[6] and the National Heart Lung and Blood Institute,[7] will provide a consistent message to both women and health care providers about weight status. The new guidelines also recommend the application of the IOTF BMI cut-points to adolescents (<18 years) rather than the Centers for Disease Control and Prevention (CDC) growth chart BMI cut-points, which vary with age. This change will classify more pregnant adolescents as normal weight, rather than overweight, and they will therefore be advised to gain more weight. This change conforms to research findings showing that higher gains for adolescents, who may still be growing, produce optimal birth outcomes.[8,9]

Gestational Weight Gain Ranges

The recommended gestational weight gain ranges for women who are underweight (28–40 lb), normal weight (25–35 lb), and overweight (15–25 lb) remain unchanged from the 1990 IOM guidelines; however, there is now a specific and relatively narrow range of weight gain recommended for women who are obese (11–20 lb). Unfortunately, there are insufficient data to provide recommendations specific for women in an obesity class higher than class I (class II, BMI 35–39.9; class III, BMI 40–44.9; or class IV, BMI >45). Previous studies show that although women who are underweight tend to gain weight within their recommended range, women who are normal weight, overweight, or obese, especially, are likely to exceed them.[10] This suggests that many women will require guidance from health care providers regarding changes in diet and physical activity that are necessary for appropriate gestational weight gains.

Race-, Age-, and Height-specific Recommendations

The 1990 IOM recommendations provided weight gain ranges specific for black women, women of short stature, and adolescents. Black women and adolescents were advised to gain within the upper values of their prepregnancy BMI–specific recommended range, while women of short stature were advised to gain within the lower values. Currently, there are insufficient data to suggest that these particular subgroups require modified gestational weight gain recommendations and, as a result, they have been removed from the new IOM guidelines.

Multiple Fetuses

Provisional guidelines for weight gain among women carrying twin fetuses were based on only a few studies of a single cohort of women.[11–14] Using this small evidence base, the IOM recommends the following weight gains: 37 to 54 lb for women who are normal weight, 31 to 50 lb for women who are overweight, and 25 to 42 lb for women who are obese. For women who are underweight and pregnant with twins, and women with higher-order multiples, data are lacking to determine recommendations for optimal gestational weight gain. The IOM therefore did not propose guidelines for women who are underweight or carrying more than two fetuses. Weight gain among these women should be monitored by the health care provider and individualized to the woman's needs.

A summary of the changes from the 1990 to the 2009 IOM recommendations is shown in Table 2.

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