Insufficient or excessive weight gain during pregnancy is related to increased risks of complications for mother and child. Susana Santos (Erasmus MC), together with LifeCycle partners and other researchers around the world, developed references for weight gain during pregnancy for underweight, normal weight, overweight and obesity women. With these references the weight gain can be better monitored. For this large international study data from almost 220,000 pregnant women were used of 33 studies from Europe, North America and Oceania, including cohorts from LifeCycle partners. Click here for the app to calculate the reference values of weight gain during pregnancy.