They sure do. Being overweight and eating poorly while pregnant is a contributing factor to gestational diabetes. Even nondiabetic mothers who overeat are at risk of having a gigantic fucking baby that can't be born vaginally and now has to be delivered by cesarean, which happens to also up a kids lifetime obesity risk and chance of developing asthma and allergies (which are also risks for fat kids in general.)  It's selfish and dangerous. The food you eat actually flavors your amniotic fluid, and there is lots of research linking prenatal nutrition and childhood health and it's astonishing.