Smoking is a major public health problem. All smokers face an increased risk of lung cancer, other lung diseases, and cardiovascular and other disorders. Smoking during pregnancy can harm the health of both a woman and her unborn baby.

Currently, at least 10 percent of women in the United States smoke during pregnancy.

Statistics from the United States are compelling. According to the U.S. Public Health Service, if all pregnant women in this country stopped smoking, there would be an estimated 11 percent reduction in stillbirths and 5 percent reduction in newborn deaths.

Cigarette smoke contains more than 2,500 chemicals. It is not known for certain which of these chemicals are harmful to the developing baby, but both nicotine and carbon monoxide play a role in causing adverse pregnancy outcomes.

How can smoking harm the newborn?

Smoking nearly doubles a woman’s risk of having a low-birthweight baby. In 2004, 11.9 percent of babies born to smokers in the United States were of low birthweight (less than 5½ pounds), compared to 7.2 percent of babies of nonsmokers. Low birthweight can result from poor growth before birth, preterm delivery or a combination of both. Smoking has long been known to slow fetal growth.

Smoking also increases the risk of preterm delivery (before 37 weeks of gestation). Premature and low-birthweight babies face an increased risk of serious health problems during the newborn period, chronic lifelong disabilities (such as cerebral palsy, mental retardation and learning problems), and even death.

The more a pregnant woman smokes, the greater her risk of having a low-birthweight baby. However, if a woman stops smoking even by the end of her second trimester of pregnancy, she is no more likely to have a low-birthweight baby than a woman who never smoked.

A recent study suggests that women who smoke anytime during the month before pregnancy to the end of the first trimester are more likely to have a baby with birth defects, particularly congenital heart defects. The risk of heart defects appears to increase with the number of cigarettes a woman smokes.

Can smoking cause pregnancy complications?

Smoking is associated with a number of pregnancy complications. Smoking cigarettes doubles a woman’s risk of developing placental problems. These include:

  • Placenta previa (a low-lying placenta that covers part or all of the opening of the uterus)

  • Placental abruption (in which the placenta peels away, partially or almost completely, from the uterine wall before delivery)

Both can result in heavy bleeding during delivery that can endanger mother and baby, although cesarean delivery can prevent most deaths.

Smoking in pregnancy increases a woman’s risk of premature rupture of the membranes (PROM), when the sac that holds the baby inside the uterus breaks before completion of 37 weeks of pregnancy. Usually, when it breaks, normal labor ensues within a few hours. If the rupture occurs before 37 weeks of pregnancy, it often results in the birth of a premature baby.

Babies whose mothers smoked during pregnancy are up to three times as likely to die from sudden infant death syndrome (SIDS) as babies of nonsmokers.

Can exposure to secondhand smoke during pregnancy harm the baby?

Studies suggest that babies of women who are regularly exposed to secondhand smoke during pregnancy may have reduced growth and may be more likely to be born with low birthweight. Pregnant women should avoid exposure to other people’s smoke.

Source: March of Dimes