When a women smokes during pregnancy how is the developing baby affected?

The baby can be born prematurely to a mother who smokes. It also affects development of the fetus. I remember in one of my child development classes showed the embryonic fluid bright red due to smoking. I would think any pregnant woman would take care to help their child grow and develop to be the smartest best person they could be. What the pregnant mother does affects their child ALL of their lives.