Please use the following as a guide to help you decide which size to buy. All measurements are in centimeters. Our sizing is based on pre-pregnancy size, you should not have to size up from pre-pregnancy size. For example, if you wear a size small pre-pregnancy, you should shop for a size small, not a medium. In addition, you do not need to move up a size throughout pregnancy. Maternity clothes are intended to grow with the belly.