Pregnant women who smoke or are exposed to secondhand cigarette smoke have a greater risk of delivering a premature or low-birth-weight baby because the amount of oxygen available to the fetus is reduced, inhibiting its growth. And, of course, smoking puts your own health at risk as well. If you or your partner need help to stop smoking, talk with your doctor as soon as possible. Quitting smoking is one of the most important things you can do to ensure your baby's health.