Metabolic and behavioral changes that occur during pregnancy have well-known effects on maternal and fetal health during the immediate pregnancy and now are thought to be a catalyst for future health throughout later life. Recommendations for appropriate gestational weight gain (GWG) and lifestyle modifications during pregnancy have changed throughout history as more is known about this crucial time. Herein we discuss the current GWG recommendations and the impact of pregnancy and excess GWG gain on the current and future health of women and children including risk of obesity, gestational diabetes, type II diabetes, cardiovascular disease, and metabolic syndrome.