OBSTETRICS A systematic review of outcomes of maternal weight gain according to the Institute of Medicine recommendations: birthweight, fetal growth, and postpartum weight retention Anna Maria Siega-Riz, PhD; Meera Viswanathan, PhD; Merry-K Moos, BSN, MPH; Andrea Deierlein, MS, MPH; Sunni Mumford, SM; Julie Knaack, MPH; Patricia Thieda, MS; Linda J. Lux, MPA; Kathleen N. Lohr, PhD I deal weight gain during pregnancy has long been debated. Because preg- nancy is the only common clinical situa- tion in which the provider has at least 2 patients, the mother and the fetus, bal- ancing the amount of weight gain needed to optimize the size of the baby without jeopardizing the health of the mother, both in the short and long term, is essential. This balance has proven challenging. In the 1930s, the recommendation to all pregnant women, irrespective of pre- gravid weight status, was 6.8 kg (15 lb). This recommendation to restrict weight gains to decrease the risk of pregnancy complications continued until 1970; it stemmed largely from the observation that increased maternal weight gains were positively related to higher birth- weights. 1 In 1970, however, the Institute of Medicine (IOM) determined that re- striction of weight gain was likely to be harmful with respect to birthweight; subsequently, weight gain recommenda- tions were eased from less than 20 lb to a range of 20-27 lb. 2 Over the next 2 decades, accumulating research suggested that 1 guideline was unlikely to benefit all women and their fetuses. This recognition led an IOM committee to issue guidelines that of- fered standardized guidance to providers and to the general public based on a woman’s pregravid weight status. 3 The recommendations were weight gains of the following: (1) 28-40 lb for women with low body mass index (BMI), defined as less than 19.8 kg/m 2 ; (2) 25-35 lb for women with normal BMI (19.8-26 kg/m 2 ); and (3) 15-25 lb for women with high BMI (26.0-29.0 kg/ m 2 ). Furthermore, the recommenda- tions included a weight gain of at least 15 lb for obese women (BMI 29 kg/m 2 ), weight gain in the upper end of the rec- ommended range for adolescents and black women, and weight gain in the lower end of the recommended range for short women (157 cm or 62 in). This systematic review of outcomes of maternal weight gain, drawn from a report conducted for the Agency for Healthcare Research and Quality (AHRQ), 4 was motivated by several trends in the perinatal field that are of great public health concern. First, since 1990, women have increasingly gained weight during pregnancy beyond the thresholds set forth by the IOM 3 ; these increases are pronounced among over- weight and obese women. 5-7 Second, overweight and obesity levels among women of childbearing ages have risen dramatically. 8-11 Third, pregnancy com- plications associated with high prepreg- nancy weight such as gestational diabe- tes, large-for-gestational-age babies, 12 and cesarean delivery 13 have increased in prevalence. Fourth, overweight levels among preschool children have risen. 10 These trends suggest that excess weight gained during pregnancy may be From the Departments of Epidemiology (Drs Siega-Riz and Ms Mumford), Nutrition (Drs Siega-Riz and Ms Deierlein), and Maternal and Child Health (Ms Moos and Ms Knaack), School of Public Health, and Department of Obstetrics and Gyncecology, University of North Carolina (Ms Moos); RTI International (Drs Viswanathan and Lohr and Ms Lux), and Sheps Center for Health Services Research (Ms Thieda), University of North Carolina, Chapel Hill, NC. Received July 17, 2008; accepted July 1, 2009. Reprints not available from the authors. This study was supported in part by the Agency for Healthcare Research and Quality (Contract 290-02-0016). 0002-9378/$36.00 © 2009 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2009.07.002 This systematic review focuses on outcomes of gestational weight gain, specifically birthweight, fetal growth, and postpartum weight retention, for singleton pregnancies with respect to the 1990 Institute of Medicine weight gain recommendations. A total of 35 studies met the inclusion criteria and were reviewed. There was strong evidence to support associations between ex- cessive gestational weight gain and increased birthweight and fetal growth (large for gestational age) as well as inadequate gestational weight gain and decreased birthweight and fetal growth (small for gestational age). There was moderate evidence to support the association between excessive gestational weight gain and postpartum weight retention. Clear clinical recommen- dations based on this review are challenging because of several limitations in the literature. Improvements in future research include the use of consistent definitions of gestational weight gain and outcomes of interest, assessment of confounders, and better collection of weight and weight gain data. Key words: birthweight, fetal growth, maternal weight gain, postpartum weight retention Cite this article as: Siega-Riz AM, Viswanathan M, Moos M-K, et al. A systematic review of outcomes of maternal weight gain according to the Institute of Medicine recommendations: birthweight, fetal growth, and postpartum weight retention. Am J Obstet Gynecol 2009;201:339.e1-14. Review www. AJOG.org OCTOBER 2009 American Journal of Obstetrics & Gynecology 339.e1