First of all, up to 5% of infant deaths could be prevented if pregnant women did not smoke.
More than 10% of women smoke throughout their pregnancies − some studies put the number at 15% or higher, although it varies by age. Pregnant teens (ages 15 to 17) smoke at the highest rate, with more than 20% smoking in the past month.
Smoking is linked to an increased risk of early delivery and infant death. Babies born to smokers have a slightly higher risk of heart defects, cleft lip or palate, and possibly other birth defects compared to babies born to non-smokers. Research also suggests that babies of mothers who smoke during and after pregnancy are 3 to 4 times more likely to die from sudden infant death syndrome (SIDS) than babies born to non-smoking mothers. The risk of SIDS is somewhat less for infants whose mothers stop smoking during pregnancy, even if they start smoking again after delivery. But infants of non-smoking mothers have the lowest risk of SIDS.
Of the women who are able to stop smoking during pregnancy, half are smoking again 6 months after the delivery.
Smoking during pregnancy causes low birth-weight in at least 1 in 5 infants. This is because smoking during pregnancy slows fetal growth, often causing babies to have health problems as a result of being born underweight. Women who stop smoking before they get pregnant reduce their risk of having a low birth weight baby to that of women who never smoked. Women who quit during the first 3 to 4 months of pregnancy are less likely to have low birth-weight babies than those who keep smoking.
Many women are able to quit smoking during early pregnancy. But women who have mood disorders, such as depression, often find it much harder to quit. Researchers have learned that between one-third and one-half of women who smoke during pregnancy have a mood disorder. It can be harder for pregnant women to find treatment for depression, anxiety, or nicotine withdrawal with medicines because of concerns about the drugs hurting the fetus. Counseling or mental health therapy may help some of these women. If the woman is unable to quit smoking with therapy, she might want to talk with her doctor about other things she can try.