The Effects of Tobacco Use During and After Pregnancy on Exposed Children Relevance of Findings for Alcohol Research Marie D. Cornelius, Ph.D., and Nancy L. Day, Ph.D Alcohol and tobacco use during pregnancy have both been associated with a number of adverse effects on the growth, cognitive development, and behavior of the exposed child. Understanding the effects of prenatal tobacco exposure allows researchers to identify those characteristics that are uniquely related to tobacco and those that are affected by alcohol exposure. This research, along with studies on the effects of alcohol use during pregnancy, has implications for preventing various types of substance use during pregnancy and for treating children affected by prenatal substance use. KEY WORDS: tobacco in any form; smoking; pregnancy; adverse drug effect; postnatal AOD (alcohol or other drug) exposure; prenatal AOD exposure; infant; cognitive development; psychobehavioral AODE (effects of AOD use, abuse, and dependence); growth and development omen who smoke during the National Pregnancy and Health this issue examine the use of alcohol pregnancy are also likely to Survey (National Institute on Drug and tobacco together, this article focuses Wdrink alcohol. In one survey, Abuse [NIDA] 1996), 74 percent of on tobacco use during pregnancy and conducted as part of the Maternal Health women who used illicit drugs during the effects of prenatal tobacco expo- Practices and Child Development pregnancy also reported either smoking, sure. Understanding the effects of pre- (MHPCD) project in Pittsburgh, drinking, or both. The use of either natal tobacco exposure allows the iden- Pennsylvania, 76 percent of adult women one of these drugs is, in itself, a risk tification of those characteristics that who reported smoking during their first factor for poorer pregnancy outcome. are uniquely related to tobacco and trimester of pregnancy said that they Although alcohol and tobacco are also drank alcohol during that period frequently used together during preg- (Day et al. 1992). Among pregnant nancy, researchers studying the negative MARIE D. CORNELIUS, PH.D., is an teenagers surveyed, 61 percent of those effects of prenatal exposure to tobacco associate professor of psychiatry and who smoked during the first trimester and alcohol have generally examined epidemiology and NANCY L. DAY, PH.D., also drank alcohol (Cornelius et al. 1995). the effects of each drug separately. is a professor of psychiatry, epidemiology, In addition, tobacco and alcohol use Therefore, it is difficult to discuss the and pediatrics at the University of are both prevalent among women who effects of the combined use of the two Pittsburgh School of Medicine, Pittsburgh, use illicit drugs during pregnancy. In drugs. Although the other articles in Pennsylvania. 242 Alcohol Research & Health Tobacco Use During and After Pregnancy those that are affected by alcohol expo- Effects of Smoking During prenatal tobacco exposure was signifi- sure. This research, along with research Pregnancy cantly related to reduced birth weight, on the effects of alcohol use during birth length, head circumference, and pregnancy, has implications for preventing This section of the article reviews find- chest circumference. These reductions various types of substance use during ings on the effects of maternal smoking were even more pronounced than those pregnancy and for treating children during pregnancy on the exposed chil- found in a similar cohort of the chil- affected by prenatal substance use. dren’s growth, cognitive function, and dren of adult women (Day et al. 1992). Prenatal tobacco exposure has been behavior. The subsequent section focuses For example, in the study of adult moth- reported to be a significant risk factor on the effects of passive smoking. Because ers and their children, prenatal tobacco for sudden infant death syndrome (SIDS) of space limitations, this article does use was significantly associated with a (National Cancer Institute [NCI] 1999) not review research on the effects of reduction in birth weight of 158 grams and is estimated to be responsible for up prenatal alcohol exposure. Because per pack per day. In the children of teen- to 4,800 infant deaths as well as 61,000 women who smoke during pregnancy age mothers, prenatal tobacco exposure low-birth-weight (LBW) infants and are also likely to drink alcohol and use was significantly associated with a 26,000 infants requiring neonatal inten- other drugs, many of the studies reviewed reduction in birth weight of 202 grams sive care annually (DiFranza and Lew here controlled for prenatal alcohol per pack per day. The increased prob- 1995). In a national survey of pregnant exposure and other confounding factors, lems associated with young maternal adult women, however, 20.4 percent to determine the unique effects associ- age and poor fetal outcomes (Fraser et reported smoking cigarettes during ated with prenatal tobacco exposure. al. 1995; Ketterlinus et al. 1990), cou- pregnancy (NIDA 1996). This propor- pled with the high prevalence of smoking tion rises to about one-half for women Effects on Infant Growth among pregnant teenagers (Cornelius in lower socioeconomic populations et al. 1994), magnify the risks to chil- (Cornelius et al. 1995; Day et al. 1992). Maternal smoking during pregnancy dren of pregnant teenagers who smoke. Smoking during pregnancy is more has long been considered an important In another recent study on prenatal prevalent among Caucasian women com- risk factor for LBW. This association tobacco exposure and fetal growth, pared with African-American or Hispanic was first reported in 1957 and has been Zaren and colleagues (2000) reported women (NIDA 1996). Caucasian proven in numerous subsequent studies that the male fetus might be more women also smoke at higher levels than (Stillman et al. 1986; U.S. Department adversely affected than the female fetus. do women of other ethnicities. Women of Health and Human Services In this study, fetuses of nonsmoking, who smoke during pregnancy are less [USDHHS] 1980; Floyd et al. 1993). light smoking, and heavy smoking likely to be married, have less education, Birth weight decreases in direct propor- mothers were measured by sonograms have lower incomes, and attend fewer tion to the number of cigarettes smoked at weeks 17, 25, 33, and 37. Boys born prenatal visits compared with women (Persson et al. 1978; Yerushalmy 1971), to heavy-smoking mothers had greater who do not smoke during pregnancy and children of smokers are 150 to weight reductions, lower fat accretions, (Day et al. 1992; Cornelius et al. 1994). 250 grams lighter than are the children and smaller head circumferences when Compared with alcohol, marijuana, of nonsmokers (USDHHS 1980). compared with girls of heavy smoking and other illicit drug use, tobacco use is The reduction in infant weight is not mothers. less likely to decline as the pregnancy attributable to earlier gestation, because Two key ingredients of cigarette smoke progresses (Day et al. 2000; Cornelius infants of smokers exhibit growth retar- that are known to affect fetal growth et al. 1995). In the National Pregnancy dation at all gestational ages (NCI 1999). are carbon monoxide and nicotine. and Health Study (NIDA 1996), approx- In a recent study of neonatal body com- Carbon monoxide causes fetal hypoxia, imately two-thirds of the women who position, prenatal tobacco exposure was a reduction in the amount of oxygen smoked prior to their pregnancy con- significantly related to having less fat-free available to the fetus (USDHHS 1980; tinued smoking into the last trimester. mass, as measured by total body electri- Lambers and Clark 1996), whereas In contrast, only one-fourth of the cal conductivity (Lindsay et al. 1997). nicotine can lead to a decrease in the women who used alcohol prior to con- The authors concluded that the LBW flow of oxygen and other nutrients ception continued to drink into the of infants exposed to prenatal smoking across the placenta by constricting uter- third trimester. Women who smoke is primarily attributable to reduced fat- ine arteries (Lambers and Clark 1996). during pregnancy also continue smoking free mass or lean tissue. Birth length In addition, nicotine itself can cross the after the pregnancy (Cornelius et al. and head and chest circumference are placenta to affect the fetal cardiovascu- 1999a; Leech et al. 1999). Therefore, also reduced in infants who are prena- lar and central nervous systems (CNS) children born to women who use tally exposed to tobacco (Cornelius et al. (Stillman et al. 1986). Other constituents tobacco during pregnancy are likely to 1995; Day et al. 1992; Lindsay et al. of tobacco smoke (e.g., cadmium and continue to be exposed to tobacco after 1997; Luciano et al. 1998). toluene) have also been shown to cause birth. This environmental, or passive, In a recent study of pregnant teenagers fetal growth retardation (Office of exposure may also affect the children’s (Cornelius et al. 1995, 1999b), more Environmental Health Hazard Assesment development. than one-half of whom were smokers, [OEHHA] 1996). Vol. 24, No. 4, 2000 243 Long-Term Effects on Growth up at 18 months and 6 years, prenatal children whose mothers smoked dur- tobacco exposure was not related to ing pregnancy, compared with children The effects of prenatal tobacco expo- any growth reductions after controlling whose mothers did not smoke. Re- sure on older children’s growth are not for the appropriate covariates (Day et searchers evaluating the MHPCD cohort as clear as the effects on infants. Using al. 1994). Similarly, Vik and colleagues of 6-year-old children of teenage moth- data from the Collaborative Perinatal (1996) found that the reductions in ers also found a positive association Project, Naeye (1981) detected a small birth weight that were attributed to pre- between prenatal tobacco exposure and difference in height and head circum- natal tobacco exposure were not evident increased skinfold thickness. Prenatally ference in exposed children at age 7.