Weight gain in pregnancy depends on all of the following factors, except:

Smoking doesn't cause significant weight gain during pregnancy. Higher incidence of low-bih weight infants are seen with heavy smoking pregnant women. There is an increased risk of IUGR, placenta pre, placenta accreta, preterm bih, low bih weight and perinatal moality for pregnant women with smoking. Ref: Naomi E. Stotland, MD; Aaron B. Caughey, MD, MPP, MPH; Barbara Abrams, DrPH. WIC nutrition risk criteria: a scientific assessment - By Institute of Medicine (U.S.). Committee on Scientific Evaluation of WIC Nutrition Risk Criteria; Influence of pregnancy weight on maternal and child health: workshop repo ; Page 33 - 42 By Committee on the Impact of Pregnancy Weight on Maternal and Child Health, National Research Council (U.S.). Board on Children, Youth, and Families, Institute of Medicine (U.S.). Food and Nutrition Board.