The adverse effects of cigarette smoking on reproductive health are well documented. Cigarette smoking affects all stages of reproduction—from conception through delivery. Research has shown that smoking impairs fertility, leads to various complications during pregnancy, and increases the risk of fetal and neonatal death. In addition, evidence suggests that maternal smoking continues to affect children negatively throughout their childhood. Despite widespread knowledge of the adverse consequences of smoking on both mothers and children, an alarming number of women of reproductive age continue to smoke. The Third National Health and Nutrition Examination Survey (NHANES III) estimated the prevalence of parental smoking and maternal smoking during pregnancy in the United States from 1988 to 1994 (Gergen, Fowler, Maurer, Davis, & Overpeck, 1998). The study examined a representative sample of 7,680 children 2 months through 5 years of age. Based on parental reports of household smoking and maternal smoking during pregnancy, approximately 38% of children were exposed to secondhand smoke in the home and 23.8% were exposed to maternal smoking during pregnancy. If these results are generalized to the entire United States population, approximately one out of four pregnant women continue to smoke during pregnancy. Such behavior results in annual medical expenditures of approximately $4.6 billion (Aligne & Stoddard, 1997).

This packet provides information on the direct effects of maternal smoking on all aspects of reproductive health, including contraception, fertility, the growth of the fetus, delivery, health effects in early infancy, and long-term consequences. The effects of environmental tobacco smoke (ETS) on prenatal and infant health will also be examined. In addition, in recognition of the fact that smoking cessation is an extremely arduous endeavor for pregnant and non-pregnant women alike, an overview of effective cessation techniques is presented.

Smoking poses a variety of reproductive health risks even before a woman conceives. In particular, women who use birth control pills as a means of pregnancy prevention increase their risk of serious health problems if they also smoke. The Pill has some rare, but serious health risks; namely, blood clots in the legs that can travel to the lungs and heart and may lead to heart attack or stroke. This risk is greatest in women over age 35 who smoke, particularly those women who smoke 15 or more cigarettes a day. Women who fall into this category are 40 times more likely to have a heart attack than women who do not smoke or take the Pill. Evidence suggests that quitting smoking greatly reduces the risk of serious side effects associated with use of the Pill (Planned Parenthood Federation of America, 1998).

Multiple studies suggest that smoking also decreases fertility in both women and men (U.S. Department of Health and Human Services, 1980). Female smokers are approximately 3.4 times more likely than non-smoking females to take longer than a year to conceive (Cook, Petersen, & Moore, 1992). In addition, women who smoke more than a pack and a half of cigarettes a day have a 43 percent lower fertility rate than nonsmokers. Female smokers are also more likely to experience irregular menses, early menopause, and non-menstrual vaginal bleeding. Research suggests that smoking may also affect male fertility. Sperm production and mobility, as well as secretion of male hormones are all reduced in male smokers (Cook et al., 1992; US DHHS, 1980; US DHHS, 1990). Some evidence indicates a positive relationship between the number of abnormally formed sperm and the number of cigarettes smoked—as cigarette smoking increases, so do the number of abnormally formed sperm. Smoking may also interfere with fertilization, though further data is required to substantiate this observation.

The mechanisms through which fertility is affected are uncertain. It is possible that the nicotine from cigarette smoke interferes with the release of hormones from the hypothalamus or pituitary that are responsible for stimulating reproductive hormones. In females, smoking may actually result in a depletion of ova (US DHHS, 1990). In male smokers, cigarette smoke may act directly on the testes, interfering with sperm production (US DHHS, 1980).

The cigarette smoke inhaled by the mother directly affects the growing fetus. Cigarette smoke contains carbon monoxide, which decreases the amount of oxygen in the mother’s blood. Because blood flows from the mother through the umbilical cord to the fetus, the fetus is dependent on the mother for a supply of oxygen—when a mother smokes, the supply of oxygen to the fetus is reduced. The nicotine contained in cigarette smoke also increases the mother’s heart rate, causing her blood vessels to narrow. As the mother’s blood vessels constrict, the flow of blood through the umbilical cord is reduced, directly affecting the fetus (QUIT Health Promotion Services, 1997). Elevated concentrations of other toxic chemicals that reside in cigarette smoke, such as benzo(a)pyrene, cyanide, thiocyanate, and cadmium have also been found in the blood and urine of maternal smokers. Such chemicals may interfere with the growth of the fetus and contribute to low birth weight (US DHHS, 1980).

Exposure to carbon monoxide and reduced blood flow has a variety of consequences for the developing fetus and during delivery. First, babies born to women who smoke during pregnancy are approximately 200 grams lighter than babies born to nonsmokers (US DHHS, 1980). This relationship is independent of all other factors that may exert an influence on birth weight, including ethnicity, socioeconomic status, and maternal size, among other factors. In addition, birth weight is affected by the amount of cigarettes smoked by the mother during pregnancy—"the more the woman smokes during pregnancy, the greater the reduction in birth weight" (US DHHS, 1980, p. 194). Although birth weight may be reduced by smoking, there is little evidence to suggest that placental weight is affected. However, the ratio between birth weight and placental weight is larger in smokers than in nonsmokers. This increased ratio reflects a decrease in birth weight and a slight increase in placental weight. Low birth weight is one of the primary causes of infant mortality.

Although smoking may cause an increased risk of low birth weight, premature births are not as common. Researchers that have examined this phenomenon have found that while smokers’ babies are smaller than nonsmokers’ babies across all dimensions (length, and head, chest, and shoulder circumference), mean length of gestation is similar for smokers and nonsmokers (US DHHS, 1980). However, maternal smoking during pregnancy is associated with an increase in premature detachment of the placenta, abnormal placental attachment to the uterus, abnormal vaginal bleeding, and ruptured membranes—all of these complications greatly increase the risk of fetal and neonatal death (Cook et al., 1992). In addition to the aforementioned pregnancy complications, maternal smoking is associated with higher rates of spontaneous abortion. As level of smoking increases, so does the risk of spontaneous abortion. Maternal smoking may also be related to risk of tubal pregnancy, but the data remain inconclusive (US DHHS, 1990).

Maternal smoking continues to affect the newborn child throughout infancy. Infants born to maternal smokers are more likely to die before their first birthday than are infants born to nonsmokers (Cook, et al., 1992). The higher rate of infant mortality amongst children of mothers who smoke is primarily due to respiratory illness and sudden infant death syndrome (SIDS). Ample evidence suggests that maternal smoking during pregnancy is strongly related to incidence of sudden infant death. A recent study examined the relationship between maternal smoking and SIDS in the United States and Sweden from 1990-1991 (MacDorman, Cnattingius, Hoffman, Kramer, & Haglund, 1997). The researchers found that SIDS rates increased with the amount of cigarettes smoked by the mother. SIDS rates were highest for women who smoked 10 or more cigarettes per day, followed by women who smoked 1-9 cigarettes per day. Nonsmoking women had the lowest rate of SIDS.

Children of smokers are also hospitalized more frequently, visit the doctor more often, and stay in the hospital for a greater length of time than children of nonsmokers (US DHHS, 1980). The increased rate of hospitalization and physician visitation is due primarily to respiratory diseases, such as bronchitis and pneumonia. However, it is important to consider that once the child is born, it is difficult to distinguish between the effects of maternal smoking during and after pregnancy. For example, is the increased rate of respiratory illness due to the effects of maternal smoking during pregnancy, or does it result from environmental tobacco smoke inhaled by the child during infancy? Despite this uncertainty, it is apparent that maternal smoking exerts an adverse impact at every stage of child development. The negative health effects of secondhand smoke will be discussed in more detail in the section on Exposure to Environmental Tobacco Smoke.

The infant is also affected by maternal smoking through breast-feeding. First, mothers who smoke are less likely to breast-feed their infants, thus depriving them of the nutritional benefits of breast milk. However, those maternal smokers who do breast-feed transmit nicotine through their breast milk to the infant. There is some evidence that nicotine inhibits milk production and reduces the amount of vitamin C present in breast milk (Cook et al., 1992).

 Maternal smoking is associated with a variety of adverse developmental outcomes. However, as previously discussed, it is not always apparent whether the negative consequences result from fetal exposure to cigarette smoke or passive inhalation of environmental tobacco smoke after birth. Maternal smoking during pregnancy has been linked to childhood predisposition to respiratory infection (Jedrychowski & Flak, 1997), deficient childhood lung function (Cunningham, Dockery, & Speizer, 1994), childhood behavioral difficulties, including conduct disorder and attention deficit disorder (Fergusson, Horwood, & Lynskey, 1993; Moore, 1997; Orlebeke & Verhulst, 1997), idiopathic mental retardation (Drews, Murphy, Yeargin-Allsopp, & Decoufle, 1996), and childhood asthma and wheezing (Hu, Persky, Flay, Zelli, Cooksey, & Richardson, 1997), though further research is required to verify these findings. Also, children of mothers who smoke are more likely to become smokers themselves (Kandel, Wu, & Davies, 1994). Studies examining the effects of maternal smoking on childhood cognitive ability, childhood cancer, and development of oral cleft defects remain inconclusive (Fergusson & Lloyd, 1991; Klebanoff, Clemens, & Read, 1996; Werler, Lammer, Rosenberg, & Mitchell, 1990).

 ETS, also known as "secondhand smoke," is derived from a mixture of side-stream smoke (SS) and mainstream smoke (MS). SS is comprised of the smoke that diffuses directly from the burning tobacco into the atmosphere, while MS consists of the smoke exhaled by the smoker. Most tobacco smoke in the environment is comprised of SS, which contains higher levels of toxic compounds than MS (US EPA, 1992; NHMRC, 1997). Although the ETS inhaled by children is dilute compared to the mainstream smoke inhaled by parental smokers, research has shown that the two types of smoke are chemically similar (US EPA, 1992). Approximately 50 known carcinogens are present in tobacco smoke. Some of the toxic chemicals and carcinogens that reside in ETS include hydrogen cyanide, sulfur dioxide, benzene, formaldehyde, nicotine, and carbon monoxide (California EPA, 1997).

In 1992, as the result of an extensive review of the literature on ETS, the U.S. Environmental Protection Agency classified ETS as a known (Group A) human carcinogen (US EPA, 1992). According to the EPA, approximately 3,000 lung cancer deaths each year in the United States are attributable to the effects of passive smoking (US EPA, 1992). ETS is linked to a variety of childhood disorders, including lower respiratory tract infection, exacerbation of pre-existing asthma, development of asthma in previously non-asthmatic children, sudden infant death syndrome (SIDS), middle ear disease, and possibly some types of childhood cancer. A recent study examined the medical expenditures associated with parental smoking. The researchers estimated that approximately 8% of total pediatric medical spending, or about $58 billion annually, may be attributable to parental smoking (Aligen & Stoddard, 1997).

Additional evidence suggests that fetal exposure to ETS in the household has harmful effects. When nonsmoking pregnant women are exposed to ETS, they inhale the carbon monoxide, nicotine, and other chemicals present in sidestream and mainstream smoke. These chemicals pass through the bloodstream and into the placenta, thus reducing oxygen supply to the fetus. Supplementary information on the health effects of passive smoking on infants and children may be obtained from the World Health Organization. For more information on environmental tobacco smoke, see Environmental Tobacco Smoke (ETS): An Overview. 

There are a lot of good reasons for pregnant women and their partners to quit smoking. As the research cited in this packet indicates, smoking poses a variety of health risks for the adults who smoke, the developing fetus, and the growing infant and child. Because of the effects of smoking on fertility, the best time for a woman and her partner to quit smoking is several months prior to conception. If a woman intends to become pregnant in the near future, she will increase her chances of conceiving if she and her partner both quit smoking.

Smoking cessation is not an easy endeavor. Nicotine is a highly addictive substance and individuals who attempt to quit may notice strong, physiological cravings for cigarettes. Cigarettes are also psychologically addictive. Individuals may associate smoking with pleasurable and relaxing situations, or they may smoke for social reasons. However, a variety of behavioral techniques exist that ease the cessation process for those women who do not plan to join a formal cessation program (see American Lung Association; March of Dimes Birth Defects Foundation). A number of standardized cessation programs also exist. For example, the University of Texas Center for Health Promotion Research and Development created a comprehensive 8-week smoking cessation program targeting pregnant women (1993).

For more information on smoking cessation during pregnancy, see Ershoff, Quinn, Mullen, and Lairson (1990); Mullen (1990); Mullen, Carbonari, Tabak, and Glenday (1991); Mullen, Quinn, and Ershoff (1990); Quinn, Mullen, and Ershoff (1991); and Smoking Cessation: An Overview.

1. Aligne, C.A., & Stoddard, J.J. (1997). Tobacco and children: An economic evaluation of the medical effects of parental smoking. Archives of Pediatrics and Adolescent Medicine, 151, 648-653.

 

2. Australian National Health and Medical Research Council. (1997). The health effects of passive smoking. Canberra, Australia: Australian Government Publishing Service.

 

3. California Environmental Protection Agency, Office of Environmental Health Hazard Assessment. (1997). Health effects of exposure to environmental tobacco smoke. Sacramento, CA: Author.

 

4. Center for Health Promotion Research and Development, The University of Texas School of Public Health. (1993). Stop smoking! A special program for pregnant women. Santa Cruz, CA: ETR Associates.

 

5. Cook, P.S., Petersen, R.C., & Moore, D.T. (1992). Alcohol, tobacco, and other drugs may harm the unborn. T.B. Haase (Ed.) Rockville, MD: U.S. Department of Health and Human Services. DHHS Publication No. (ADM) 92-1711.

 

6. Cunningham, J., Dockery, D.W., & Speizer, F.E. (1994). Maternal smoking during pregnancy as a predictor of lung function in children. American Journal of Epidemiology, 139 (12), 1139-1152.

 

7. Drews, C.D., Murphy, C.C., Yeargin-Allsopp, M., & Decoufle, P. (1996). Relationship between idiopathic mental retardation and maternal smoking during pregnancy. Pediatrics, 97 (4), 547-553.

 

8. Ershoff, D.H., Quinn, V.P., Mullen, P.D., & Lairson, D.R. (1990). Pregnancy and medical cost outcomes of a self-help prenatal smoking cessation program in a HMO. Public Health Reports, 105 (4), 340-347.

 

9. Fergusson, D.M., Horwood, L.J., & Lynskey, M.T. (1993). Maternal smoking before and after pregnancy: Effects on behavioral outcomes in middle childhood. Pediatrics, 92 (6), 815-822.

 

10. Fergusson, D.M., & Lloyd, M. (1991). Smoking during pregnancy and its effects on child cognitive ability from the ages of 8 to 12 years. Paediatric and Perinatal Epidemiology, 5 (2), 189-200.

 

11. Gergen, P.J., Fowler, J.A., Maurer, K.R., Davis, W.W., & Overpeck, M.D. (1998). The burden of environmental tobacco smoke exposure on the respiratory health of children 2 months through 5 years of age in the United States: Third National Health and Nutrition Examination Survey, 1988 to 1994. Pediatrics, 101 (2).

 

12. Hu, F.B., Persky, V., Flay, B.R., Zelli, A., Cooksey, J., & Richardson, J. (1997). Prevalence of asthma and wheezing in public school children: Association with maternal smoking during pregnancy. Annals of Allergy, Asthma, and Immunology, 79 (1), 80-84.

 

13. Jedrychowski, W., & Flak, E. (1997). Maternal smoking during pregnancy and postnatal exposure to environmental tobacco smoke as predisposition factors to acute respiratory infections. Environmental Health Perspectives, 105 (3), 302-306.

 

14. Kandel, D.B., Wu, P., & Davies, M. (1994). Maternal smoking during pregnancy and smoking by adolescent daughters. American Journal of Public Health, 84 (9), 1407-1413.

 

15. Klebanoff, M.A., Clemens, J.D., & Read, J.S. (1996). Maternal smoking during pregnancy and childhood cancer. American Journal of Epidemiology, 144 (11), 1028-1033.

 

16. MacDorman, M.F., Cnattingius, S., Hoffman, H.J., Kramer, M.S., & Haglund, B. (1997). Sudden infant death syndrome and smoking in the United States and Sweden. American Journal of Epidemiology, 146, 249-257.

 

17. Moore, P. (1997). Smoking in pregnancy linked with conduct disorder. Lancet, 350 (9072), 190.

 

18. Mullen, P.D. (1990). Smoking cessation counseling in prenatal care. In I.R. Merkatz, J.E. Thompson, P.D. Mullen, & R.L. Goldenberg (Eds.). New Perspectives on Prenatal Care. New York: Elsevier.

 

19. Mullen, P.D., Carbonari, J.P., Tabak, E.R., & Glenday, M.C. (1990). Improving disclosure of smoking by pregnant women. American Journal of Obstetrics and Gynecology, 165 (2), 409-413.

 

20. Mullen, P.D., Quinn, V.P., & Ershoff, D.H. (1990). Maintenance of nonsmoking postpartum by women who stopped smoking during pregnancy. American Journal of Public Health, 80 (8), 992-994.

 

21. Orlebke, J.F., & Verhulst, F.C. (1997). Increase in child behavior problems resulting from maternal smoking during pregnancy. Archives of Environmental Health, 52 (4), 317-321.

 

22. Planned Parenthood Federation of America. (1998). Smoking or the Pill. [On-line]. Available: Internet. File: http://www.plannedparenthood.org/birth-control/SMOKING.HTM

 

23. Quinn, V.P., Mullen, P.D., Ershoff, D.H. (1991). Women who stop smoking spontaneously prior to prenatal care and predictors of relapse before delivery. Addictive Behaviors, 16, 29-40.

 

24. QUIT Health Promotion Services, Health Department of Western Australia. (1997). Smoking and pregnancy. [On-line]. Available: Internet. File: http://www.public.health.wa.gov.au/hp4613.htm

 

25. Redhead, C.S., & Rowberg, R.E. (1995). Environmental tobacco smoke and lung cancer risk. Washington, DC: Congressional Research Service/The Library of Congress.

 

26. U.S. Department of Health and Human Services. (1980). The health consequences of smoking for women: A report of the Surgeon General. Rockville, MD: U.S. Department of Health and Human Services, Public Health Service, Office of the Assistant Secretary for Health, Office on Smoking and Health.

 

27. U.S. Department of Health and Human Services. (1990). The health benefits of smoking cessation: A report of the Surgeon General. Rockville, MD: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health. DHHS Publication No. (CDC) 90-8416.

 

28. United States Environmental Protection Agency. (1992). Respiratory health effects of passive smoking: Lung cancer and other disorders. Washington, DC: Author.

 

29. Werler, M.M., Lammer, E.J., Rosenberg, L., & Mitchell, A.A. (1990). Maternal smoking during pregnancy in relation to oral clefts. American Journal of Epidemiology, 132 (5), 926-932.