Can diabetes affect pregnancy?

Certainly: In women with gestational diabetes and type 2 diabetes, the sugar in your blood directly affects the size of your baby. If your blood sugar level is high, the baby gets too much nourishment and overgrows. This can lead to a condition called macrosomia or "fat" baby. Macrosomia causes problems for both you and your baby.

Yes: The fetus will eventually make it's own insulin & control its glucose levels but if mother is poorly controlled her high sugar levels cause problems. Every tissue & organ within baby can end up overgrown & some will develop birth defects. Tight control of blood sugar levels reduce the risk. Babies excess insulin can cause low sugars at birth requiring IV glucose for extended periods.