A pregnant woman provides all the food a baby needs during the pregnancy. Everything she eats, drinks and breathes, including tobacco smoke, affects her and the baby. It's hard for pregnant women to stop smoking if they have a partner who smokes. Couples who quit together are more likely to be successful than if they try alone.
It helps if dad quits, too. Passive smoking during pregnancy increases the risk of a range of pregnancy problems and birth defects, and can affect the development of your baby's brain.