Efforts to prevent damage to the fetus have often focused on preventing alcohol use during pregnancy. However, another addictive drug -- nicotine -- affects the developing fetus in significant ways that warrant vigorous intervention.

Smoking, according to a former U.S. Surgeon General, is probably the single most important modifiable cause of poor pregnancy outcome. Experts in many disciplines agree that smoking during pregnancy affects the health of the fetus and the newborn.

Studies over the past 20 years document many health effects of maternal smoking during pregnancy: significantly lower birth weight, a higher incidence of miscarriages, respiratory problems, and other complications. Some studies link maternal smoking with attention deficit disorder, decreased bone density, and functional disturbances in the nervous system. One recent study found that maternal smoking during pregnancy was related to persistent criminal activity in adult male offspring.

Studies have consistently shown a 150 to 200 gram (5.25 to 7 ounce) deficit in the birth weight of term infants of mothers who smoke compared with those of non-smokers, said Suzanne Cliver, PhD, a research instructor at the University of Alabama, Birmingham, and a noted researcher on smoking and pregnancy. Low birth weight is associated with an increased risk of developmental delays.

A review of 25 studies that compared perinatal death rates of women who smoked vs. those who did not suggests that 3.4 to 8.4 percent of perinatal deaths (stillborn infants or deaths shortly after birth) occur each year due to maternal smoking. According to Richard Windsor, PhD, principle investigator of the Smoking Cessation and Reduction in Pregnancy Trial (SCRIPT) at the University of Alabama, Birmingham, Carbon monoxide inhaled when smoking causes intrauterine growth retardation and nicotine causes brain cell damage.

It is well known that drinking alcohol during pregnancy can cause fetal alcohol syndrome. In both cases, tobacco or alcohol use, it's best to eliminate all use because any exposure is going to hurt the fetus, Windsor said.

National government surveys estimate the rate of women who smoke during pregnancy is 14 to 20 percent. Of women on medicaid, 30 to 35 percent smoke during pregnancy, and 40 percent of all births are born to women on medicaid.

Passive smoking also affects the health of the fetus and newborn. Many studies have reported a two- to three-fold increase in the risk of Sudden Infant Death Syndrome (SIDS) among newborns of smoking mothers. When someone other than the mother in the household smokes, a reduction in birth weight of 25 to 50 grams can result. When both the mother and another person in the household smoke, morbidity and birth weight problems are amplified.

Prevention and smoking cessation strategies are needed for pregnant women and all women of child-bearing age. Windsor has worked in partnership with the Alabama Bureau of Health Services, Alabama Department of Public Health, to assess the feasibility of intervention approaches. Both standard and specially tailored intervention increases smoking cessation. Standard intervention involves maternity care staff (physician, nurse, midwife, social worker) asking if a woman smokes, advising her to quit, and providing information about consequences. In the medicaid group, this approach resulted in 8 percent of the women quitting. Tailored intervention, which involves specialized training of maternity care staff and self-help guides for women, resulted in a 15 to 20 percent decrease in smoking. The more intervention education women receive from maternity care providers the more likely they are to quit smoking.

Pregnancy motivates women to quit, adds Windsor. A University of Texas School of Public Health study concluded that as many as 40 percent of women who smoked prior to pregnancy quit by themselves. Light smokers are more successful in quitting than heavy smokers, indicating the need for more intense interventions for heavy-smoking women.

Smoking during pregnancy produces a variety of effects throughout the gestational period. However, according to Windsor, if pregnant women stop smoking in the first trimester, birth weight will be similar to that of babies of women who don't smoke. There's a benefit to quitting at any time during pregnancy, for both mom and the newborn, he adds.

--Published April 26, 1999