Helping women attain recommended weight gain during pregnancy is an important challenge for clinicians. It is well documented that both insufficient and excessive maternal weight gain are associated with adverse pregnancy outcomes ( (1) Subcommittee on the Nutritional Status and Weight Gain During Pregnancy, Institute of Medicine, National Academy of Sciences. Nutrition During Pregnancy, Weight Gain, Nutrient Supplements. National Academy Press, Washington, DC1990 Google Scholar , (2) Johnson J.W. Yancey M.K. A critical review of the new recommendations for weight gain in pregnancy. Am J Obstet Gynecol. 1996; 174: 254-258 Google Scholar , (3) The Federal-Provincial Subcommittee on Nutrition.Nutrition in Pregnancy. Minister of National Health and Welfare, Ottawa, Ontario, Canada1987 Google Scholar , (4) Bianco A.T. Smilen S.W. Davis Y. Lopez S. Lapinski R. Lockwood C.J. Pregnancy outcome and weight gain recommendations for the morbidly obese woman. Obstet Gynecol. 1998; 91: 97-102 Google Scholar , (5) Edwards L.E. Hellerstedt W.L. Alton I.R. Story M. Himes J.H. Pregnancy complications and birth outcomes in obese and normal-weight women effects of gestational weight change. Obstet Gynecol. 1996; 87: 389-394 Google Scholar , (6) Abrams B. Carmichael S. Selvin A. Factors associated with the pattern of maternal weight gain during pregnancy. Obstet Gynecol. 1995; 86: 170-176 Google Scholar , (7) Abrams B. Selvin S. Maternal weight gain patterns and birth weight. Obstet Gynecol. 1995; 86: 163-169 Google Scholar , (8) Seiga-Riz A.M. Adair L.S. Hobel C.J. Institute of Medicine maternal weight gain recommendations and pregnancy outcome in a predominantly Hispanic population. Obstet Gynecol. 1994; 84: 565-573 Google Scholar , (9) Shepard M.J. Hellenbrand K.G. Bracken M.B. Proportional weight gain and complications of pregnancy, labor, and delivery in healthy women of normal weight prepregnancy stature. Am J Obstet Gynecol. 1986; 155: 947-954 Google Scholar , (10) Garbaciak J.A. Richter M. Miller S. Barton J.J. Maternal weight gain and pregnancy complications. Am J Obstet Gynecol. 1985; 1525: 238-245 Google Scholar , (11) Brown J.E. Jacobson N.H. Askue L.H. Peick M.G. Influences of pregnancy weight gain on the size of infants born to underweight women. Obstet Gynecol. 1981; 57: 13-17 Google Scholar , (12) Abrams B. Laros R.K. Prepregnancy weight, weight gain and birth weight. Am J Obstet Gynecol. 1979; 154: 503-509 Google Scholar , (13) Edwards L.E. Alton I.R. Barrada I.M. Hakanson E.Y. Pregnancy in the underweight woman. Am J Obstet Gynecol. 1979; 135: 297-301 Google Scholar , (14) Naeye R.L. Weight gain and the outcome of pregnancy. Am J Obstet Gynecol. 1979; 135: 39 Google Scholar ). Insufficient gain is linked to low infant birth weight and perinatal mortality, whereas excessive gain is associated with high infant birth weight and mortality, cesarean section, and prolonged second stage of labor. This work was supported by the Fonds de Développement of the University of Montreal, the Interdisciplinary Health Research Group of the University of Montreal, the Fonds de recherche en sauté du Québec, and the Research Center of the Centre Hospitalier de I’Université de Montréal, Notre-Dame Hospital. Part of this work was the topic of C. Chabot's master's degree thesis at the University of Montreal.