It doesn't have much to do with your pre-pregnancy size, but how you carry the baby, and that will depend on the way the baby is lying in your belly, as well as your skeletal structure and what space you have in your abdomen. You may carry all out front, whereas someone else may carry to the sides, and have a wider bump but hardly anything out front.i no lots of girls that were the same size as me before they were pregnant (size 8) and they hardly had bumps till about 33 weeks