Maternal weight gain is closely monitored during pregnancy because as weight gain increases, so does the risk of excess postpartum weight retention, diabetes, and high blood pressure. While lower weight gain may prevent these complications, it also increases the risk of poor fetal growth and stillbirth. Pregnancy weight gain recommendations that balance these risks are important. The goal of this project is to establish the optimal range of pregnancy weight gain for Canadian women. We will use existing medical records from approximately 560,000 women who delivered in BC between 2004 and 2018. We will obtain information on pregnancy weight gain, and link this with short- and longer-term health complications for mother and newborn, such as excess postpartum weight retention, maternal diabetes and heart disease, poor fetal growth, and stillbirth. We will use statistical models that enable us to consider all health complications at the same time, while accounting for the fact that some complications are more serious than others. Our findings could provide the basis for new public health recommendations on pregnancy weight gain, which could help to reduce overweight and obesity in Canadian mothers and their children.