There is a growing epidemic of obesity in the United States: nearly one-third of all adults are classified as obese, and this proportion has dramatically increased during the last two decades (Flegal et al., 2002; Hedley et al., 2004).1 Women are leading the epidemic at a current prevalence rate of obesity of 33 percent (National Center for Health Statistics, 2004; Ogden et al., 2006).
Given the environment of overweight and obesity in the United States, the implications of this epidemic for women of childbearing age are of a concern. Data from the March of Dimes Perinatal Data Center indicate that in 2003, 19.6 percent of U.S. women of reproductive age were obese (March of Dimes, 2004). Obesity in women can cause serious pregnancy-related complications, but women can also modify their weight.
Past efforts to advise women on weight for pregnancy (before, during, and after) have focused little on maternal obesity. Rather, most of the attention has been devoted to concerns about low birth weight deliveries in addition to other maternal and infant outcomes. Maternal Nutrition and the Course of Pregnancy, a 1970 report of the Food and Nutrition Board of the National Research Council (NRC)2 (National Research Council, 1970),
laid the foundation for work over the next two decades, and in 1974, the U.S. Department of Agriculture established the Special Supplemental Food Program for Women, Infants, and Children to address the needs of women and children at nutritional risk.
In 1990 the Institute of Medicine (IOM) report Nutrition During Pregnancy recommended guidelines for weight gain during pregnancy based on prepregnancy maternal body mass index (BMI). Two other reports quickly followed: Nutrition During Lactation (1991) and Nutrition During Pregnancy and Lactation: An Implementation Guide (1992).
By this time, the Maternal and Child Health Bureau of the U.S. Department of Health and Human Services had also begun to address concerns about maternal weight gain. And in 1998, the National Heart, Lung, and Blood Institute (NHLBI) released its own classification of overweight and obesity by BMI (National Heart, Lung, and Blood Institute, 1998). The NHLBI classifications differed slightly from the 1990 IOM maternal BMI criteria. However, a common stimulus for all of these earlier efforts was the incidence of low birth weight deliveries, which was in part attributed to insufficient nutrition and insufficient weight gain during pregnancy.
Since publication of the 1990 IOM recommendations for weight gain during pregnancy, tremendous changes have occurred in the demographic and epidemiological profile of women experiencing pregnancy. More women entering pregnancy are either overweight or obese, and more women are entering their pregnancies with chronic conditions that lead to increased morbidity during their postpregnancy years. High rates of overweight and obesity are especially common in minority populations that may be already at risk for poor maternal and child health outcomes. Collectively, these trends have prompted concern about the adequacy of existing guidelines for weight gain during pregnancy, particularly for women who are overweight, underweight, short in stature, or adolescents.
Despite the availability of the IOM recommendations and an effort to publicize their availability, their use and compliance are not understood. As researchers have begun to address some of the issues raised in the 1990 IOM report, gaps in knowledge have emerged, even as additional data are collected and reported.
This convergence of factors prompted the NRC and the IOM to organize a workshop on maternal weight gain (before, during, and after pregnancy) and its influence on maternal and child health. With support from the Maternal and Child Health Bureau in the U.S. Department of Health and Human Services, the NRC-IOM Board on Children, Youth, and Families, in collaboration with the IOM Food and Nutrition Board, convened a committee of experts at a day and a half workshop in May 2006 to examine the current state of knowledge and highlight key observations that could form the basis for future study and deliberations regarding
maternal weight gain during pregnancy (see the Appendix for the full workshop agenda and list of participants). The workshop sought to address five questions:
What research and databases describe the distribution of maternal weight (prior to, during, and after pregnancy) among different populations of women in the United States?
What research and databases inform understanding of the effects of different weight patterns (including underweight and overweight) during pregnancy on maternal and child health outcomes (up to 12 months)?
What research has been conducted to describe the individual, community, and health care system factors that impede or foster compliance with recommended gestational weight guidelines (prior to, during, and after pregnancy)?
What opportunities exist for Title V maternal and child health programs to build on this knowledge to help childbearing women achieve and maintain recommended weight (prior to, during, and after pregnancy)?
What future research and data collection efforts could improve the efforts of Title V programs to support women from different racial and ethnic backgrounds in their efforts to comply with recommended weight guidelines and to improve their maternal health?
Throughout the workshop, the term “maternal weight gain” was used to refer to weight gain during different time periods of a woman’s life (Box 1-1). It must be noted that in longitudinal studies and studies of women with multiple pregnancies, various terms may be used interchangeably in reference to a specific pregnancy. A woman whose second preg-
Maternal Weight Definitions
Prepregnancy Weight: A woman’s actual weight prior to pregnancy up to the point that pregnancy is identified.
Prepregnancy Weight Gain: A woman’s increase in weight from some prior time until pregnancy.
Gestational Weight Gain: Amount of weight gained during the pregnancy.
Postpartum Weight Retention: Amount of weight gained during pregnancy (i.e., gestational weight gain) that the woman has at a given time point postpartum.
Postpartum Weight Gain: Weight that is gained following pregnancy.
nancy is the focus of study, then, may have weight gained between the two pregnancies described as weight retention (from the first pregnancy), postpartum weight gain (which would also be prepregnancy weight gain in reference to the second pregnancy), and then gestational weight gain and weight retention connected with the second pregnancy.
This report documents the information presented in the workshop presentations and deliberations. Its purpose is to lay out the key ideas that emerged from the workshop, both for researchers interested in interdisciplinary work in this area and for those who are involved in developing strategies to promote appropriate weight before, during, and after pregnancy. The report should be viewed as only a first step in exploring opportunities to develop a synthesis of diverse research and applying this knowledge to promote appropriate weight in women of childbearing age, and it is confined to the material presented by the workshop speakers and participants. Neither the workshop nor this report is intended as a comprehensive review of what is known about maternal weight and gestational weight gain and maternal and child health outcomes, although it is a general reflection of the literature. Many additional contributors of gestational weight gain and health outcomes—such as food frequency, congenital malformations, gender of the infant, metabolic syndrome, and contraception—were not addressed in the limited time available for the workshop. A more comprehensive review and synthesis of relevant research knowledge will have to wait for further development. Although this report was prepared by the committee, it does not represent findings or recommendations that can be attributed to the committee members. Indeed, the report summarized views expressed by workshop participants and the committee is responsible only for its overall quality and accuracy as a record of what transpired at the workshop. The workshop was not designed to generate consensus conclusions or recommendations but focused instead on the identification of ideas, themes, and considerations that contribute to understanding the role of weight gain during pregnancy as well as informing strategies that might help women achieve and maintain appropriate weight. The workshop mainly considered health outcomes of public health significance for the United States and is not necessarily pertinent to other settings.
One additional topic deserves attention in presenting this overview of pregnancy weight gain studies. Various presenters referred to weight patterns measured in pounds or kilograms. In this report, all data are reported in pound measures. Data that refer to kilogram measures have been converted to pounds to allow for easier comparisons across research studies.
Following this introduction, the report includes five sections that highlight the panel presentations at the workshop: (1) trends in maternal and gestational weight, (2) determinants of gestational weight gain, (3) consequences of gestational weight gain for maternal health, (4) infant health
outcomes that ensue from maternal and gestational weight gain, and (5) a range of approaches that promote appropriate weight during and after pregnancy. The final chapter describes cross-cutting themes that emerged from the workshop presentations and discussions.
Flegal, K.M., Carroll, M.D., Ogden, C.L., and Johnson, C.L. 2002 Prevalence and trends in obesity among U.S. adults, 1999–2000. Journal of the American Medical Association 288(14):1723–1727.
Hedley, A.A., Ogden, C.L., Johnson, C.L., Carroll, M.D., Curtin, L.R., and Flegal, K.M. 2004 Prevalence of overweight and obesity among U.S. children, adolescents, and adults, 1999–2002. Journal of the American Medical Association 291(23):2847–2850.
Institute of Medicine 1990 Nutrition During Pregnancy. Washington, DC: National Academy Press.
1991 Nutrition During Lactation. Washington, DC: National Academy Press.
1992 Nutrition During Pregnancy and Lactation: An Implementation Guide. Washington, DC: National Academy Press.
March of Dimes 2004 Maternal Obesity and Pregnancy: Weight Matters. Available: http://www.marchofdimes.com/files/MP_MaternalObesity040605.pdf. [accessed August 14, 2006].
National Center for Health Statistics 2004 National Health and Nutrition Examination Survey, 1999–2002. Available: http://www.cdc.gov/nchs/pressroom/04facts/obesity.htm. [accessed August 3, 2006].
National Heart, Lung, and Blood Institute 1998 Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. (National Institutes of Health Publication 98-4083). Washington, DC: National Institutes of Health.
National Research Council 1970 Maternal Nutrition and the Course of Pregnancy. Washington, DC: National Academy Press.
Ogden, C.L., Carroll, M.D., Curtin, L.R., McDowell, M.A., Tabak, C.J., and Flegal, K.M. 2006 Prevalence of overweight and obesity in the United States, 1999–2004. Journal of the American Medical Association 295(13):1549–1555.