Smoking and Pregnancy Quiz

They weigh an average of a half-pound less and are more likely to be born early and need special care after birth, according to the CDC. Smoking nearly doubles a woman's risk of having a baby with low birth weight (less than 5.5 pounds). The average newborn weighs about 7.5 pounds. Low-birth-weight babies who are born to women who smoke are at an increased risk for illness and death.

Recent studies also suggest that smoking increases the risk for preterm delivery by about 30 percent, the CDC says. Generally, the average length of pregnancy is 40 weeks. Preterm birth is defined as an infant born before 37 weeks. According to the March of Dimes, cigarette smoke contains about 2,500 chemicals. Nicotine and carbon monoxide, the same gas that comes from car exhaust, are two of the chemicals that are believed to cause harm to the developing baby. These chemicals can prevent necessary food and oxygen from reaching the developing baby.

Children of mothers who smoke may lag behind in school and may be smaller than children whose mothers don't smoke, according to the American Lung Association. According to the U.S. Surgeon General, babies born to mothers who smoke during pregnancy and who are exposed to secondhand smoke after birth have weaker lungs. Secondhand smoke is smoke from a burning cigarette that is inhaled by a nonsmoker; it can also come from a smoker’s exhalation. A baby’s lungs and airways are small. Breathing smoke-filled air makes it difficult for the baby to breathe and can cause lung problems like pneumonia and bronchitis.

SIDS is the leading cause of death in infants younger than 12 months of age. SIDS is the unexplained death of an infant. Being around smoke is a risk factor for SIDS.

Studies suggest that regular exposure to secondhand smoke may slow down the growth of the fetus, increasing a woman's chances of having a low-birth-weight baby, the CDC says.

Babies born to women who smoke during pregnancy are likely to have birth defects such as cleft lip, which is an opening in the lip, or cleft palate, which is an opening in the roof of the mouth.

Smoking increases a woman's risk of an ectopic pregnancy, in which the embryo becomes implanted in a fallopian tube or other abnormal site instead of the uterus.

Nicotine can be transmitted to infants through breast milk.