This narrative review discusses gestational weight gain (GWG) and medical outcomes of pregnancy, including metabolic, cardiovascular, respiratory, musculoskeletal and psychiatric systems. Taken as a whole, the available evidence shows that excessive GWG increases the risk of all medical complications of pregnancy, and negatively impacts the long-term health and weight of both mothers and their offspring. Briefly, interventions to encourage appropriate GWG are discussed and readers are directed to resources to facilitate discussion of pregnancy weight.