You know that smoking isn’t good for you, but if you’re pregnant, smoking can have damaging effects on your unborn child, too — both now and long after your baby is born. In one study, published in the European Heart Journal, researchers found that children born to mothers who smoked during pregnancy have lower levels of “good” HDL cholesterol, which in turn may increase their risk of having a stroke or heart attack later in life.

But that’s far from the only risk associated with smoking and pregnancy. Women who smoke during pregnancy pass along the health dangers of smoking to their babies in literally thousands of ways. Cigarette smoke contains more than 2,500 individual chemicals, all of which can have a potential impact on the life of an unborn child. Research has shown that smoking while pregnant can have a devastating and even life-threatening impact on fetal development.

The two byproducts of smoking that have been proven to affect developing fetuses are carbon monoxide and nicotine.

  • Carbon monoxide. A lethal gas contained in cigarette smoke that interferes with the blood's ability to carry oxygen throughout the body. This can decrease fetal oxygen levels and retard the growth of the unborn child.
  • Nicotine. This is the substance in cigarettes that provides pleasure to smokers and causes them to become addicted. Nicotine interferes with oxygen delivery to the developing fetus and has other negative effects on fetal development. Nicotine easily crosses the placenta, and researchers have found nicotine concentrations in fetuses about 15 percent higher than nicotine levels found in smoking mothers. Highly concentrated levels of nicotine have been found in fetal blood, amniotic fluid, and breast milk in expectant mothers who smoke. One study found that nicotine in breast milk can disrupt a baby's ability to sleep and reduce nap times by as much as one-third.

Specific Effects of Smoking During Pregnancy

Health experts figure if all pregnant women refrained from smoking, it would lead to an 11 percent reduction in the number of stillbirths and a 5 percent decrease in newborn deaths.

The risks of smoking during pregnancy include:

  • Low birth weight. A woman who smokes during pregnancy has twice the risk of having a baby with a low birth weight. Babies with low birth weight have an increased risk of health problems, chronic disabilities, and death.
  • Complications of pregnancy. Pregnant women who smoke are twice as likely to suffer from placental abruption and placenta previa, two serious pregnancy complications that can result in heavy bleeding during birth and greatly increase the risk of death for both mother and child
  • Birth defects. Research has found that smoking during early pregnancy increases the risk of birth defects. In particular, babies of smokers seem to have congenital heart defects more often that those of nonsmokers, and the risk of heart defects seems to rise with the number of cigarettes the expectant mother smokes.
  • Sudden Infant Death Syndrome (SIDS). Smoking during pregnancy is one of the top risk factors for SIDS. The babies of smokers are up to three times more likely to die from SIDS as the babies of nonsmokers.
  • Childhood cancer. Children of mothers who smoked during pregnancy have an increased risk of all forms of cancer, including leukemia and lymphoma, studies have found.
  • Developmental disorders. Attention deficit hyperactivity disorder, also called ADHD, occurs more frequently in children of mothers who smoked. Studies have identified a range of other behavioral and cognitive problems associated with maternal smoking, including a 50 percent increase in rates of mental retardation.

Secondhand smoke also affects unborn children even if the pregnant woman herself does not smoke: Studies show that for a pregnant woman, being around people who smoke increases the risk that her child will be born at less than normal weight and have growth issues.