Nicotine is a known carcinogenic connected to a variety of health problems, yet people, including pregnant women, continue to smoke. Nicotine is highly addictive, and many women are unwilling or unable to give up their dependence on nicotine during pregnancy. Smoking while pregnant can have effects on the baby both directly, by having negative effects on fetal growth and development, and indirectly, by causing placental problems and preterm delivery.
Low Birth Weight
One of the best documented side effects of smoking in pregnancy is the decrease in birth weight of babies born to moms who smoke during pregnancy. On average, babies born to smokers weighed 200 g, or just under half a pound, less than babies of non-smoking moms, according to Krisa Van Meurs, M.D. assistant professor at Stanford University. The more cigarettes smoked, the lower the birth weight, and length is also affected.
Placenta Effects
Smoking affects the placenta, which delivers nutrients to the baby, in several ways. The incidence of placental abruption and placenta previa are both increased in smokers. Placental abruption is the premature separation of the placenta from the uterine wall; placenta previa is a placenta that implants lower on the uterine wall than normal so that it partially or completely covers the cervix. Both conditions can cause serious bleeding, often result in preterm delivery and threaten the lives of both the mother and baby. Decreased blood flow to the placenta is thought to cause placental abnormalities.
Pregnancy Loss
The rate of miscarriages and stillbirths are both increased in smokers. Smokers have a 33 percent increase in fetal death between 20 weeks of pregnancy and the first month of life compared to non-smokers. Miscarriages are also more common in early pregnancy in smokers. Decreased blood flow to the placenta due to blood vessel constriction is also thought to be the cause of increased pregnancy loss in smokers; high carbon monoxide blood levels, which reduces the available oxygen in the blood, is also considered to be a contributing factor, Cornell University explains. Ectopic pregnancies, where the pregnancy implants in the fallopian tube rather than in the uterus, is 2 to 4 times more common in smokers, according to the NYU Student Health Center.
Long-Term Consequences
There are many potential long term consequences for babies born to smoking mothers, although once an infant is born, it's difficult to tell whether complications are caused by smoking during pregnancy or exposure to second hand smoke. An increase in cognitive and behavior defects, along with a 50 percent increase in mental retardation without known cause, are noted by Dr. Van Meurs. Childhood cancers are also more common in babies born to mothers who smoked during the pregnancy. Sudden Infant Death Syndrome (SIDS) asthma and other chronic respiratory diseases are all more common in babies whose mothers smoked in pregnancy. Smoking in pregnancy is the main risk factor for SIDS, the University of Michigan states.
