Smoking during PregnancyWHEC Practice Bulletin and Clinical Management Guidelines for healthcare providers. Educational grant provided by Women's Health and Education Center (WHEC). Smoking in US women has attributed to a 600% increase in the rate of lung cancer deaths and it has also increased risk of myocardial infarction to twice that of men. Smoking cessation interventions delivered by healthcare providers markedly increase cessation rates compared with interventions with no healthcare provider involvement. Clinicians should routinely assess and intervene with adolescents on tobacco initiation and use, including offering multiple strategies for cessation. Comprehensive, individualized smoking cessation programs coupled with the use of nicotine replacement therapy when indicated and proper follow-up care can help women to stop smoking and avoid relapse. Approximately one fifth of the deaths in the United States are attributable to smoking, amounting to more than 440,000 deaths per year (1). Approximately 28% high-school girls in 2003 reported current cigarette smokers. Among daily smokers, 81% began smoking at the age 18 years or younger, with some studies reporting the average age of initiation of smoking in women to be age 12 or 13 years. The purpose of this document is to understand risks for adverse fetal health with maternal smoking during pregnancy. The perinatal complications associated with maternal tobacco use include preterm delivery, premature rupture of membranes, spontaneous abortion, ectopic pregnancy, low birth weight, intra-uterine growth restriction, placental abruption, placenta previa, still birth, and sudden infant death syndrome (SIDS). Smoking cessation and the resources available are also discussed. Screening for tobacco use can be done efficiently as a vital sign at every clinical visit. Tobacco control is one of the most rational, evidence-based policies in medicine.The Millennium Development Goals do not include an explicit target for reducing tobacco use, but this article explains how lower tobacco use could contribute to their achievement. Epidemiology:Smoking is one of the most important modifiable causes of poor pregnancy outcomes in the United States. Increased public education measures and public health campaigns in the United States have led to a decline in smoking during pregnancy. Pregnancy appears to motivate women to make lifestyle changes; approximately 46% of patients quit smoking during pregnancy. Tobacco use results in substantial medical care costs. The Centers for Disease Control and Prevention estimates the annual US costs attributable to smoking to greater than $ 50 billion, and the cost of lost productivity and earnings to be at least another $ 47 billion per year (2). An estimated 12% US women smoke during pregnancy, with rates as high as 19% for adolescents and 28% for those with 9-11 years of education. The continued use of tobacco products during pregnancy accounts for 15% of all preterm births, 20--30% of all low-birth infants, and a 150% overall increase in perinatal mortality. It is estimated that 70% of women who discontinue tobacco use during pregnancy will relapse within 1 year of childbirth. Smoking and Reproductive Health:Cigarette smoking is a casual factor for decreased fertility in women. The effects of smoking are related to lower peak serum estradiol levels during ovarian stimulation or reduced motility and ciliary function of the epithelium lining of the fallopian tube. The compounds found in tobacco smoke affect oocyte and sperm production, tubal motility, embryo cleavage, blastocyst formation, and implantation. For the women attempting in-vitro fertilization, studies have shown smokers to be approximately one half as successful as non-smokers, and diminished ovarian reserve has been suggested as a key mechanism (3). After conception, women who smoke experience higher rates of spontaneous abortion and ectopic pregnancy than non-smokers. Menstrual irregularity, secondary amenorrhea, and dysmenorrhea occur more frequently in smokers than in non-smokers. There is limited or inconsistent evidence to suggest that smoking decreases the risk for endometriosis and uterine fibroids. A protective effect is plausible because of its systemic anti-estrogenic effect, but this mechanism has not been examined extensively. Smoking is one of the most studied of human behaviors. Thousands of studies have documented its health consequences, yet most have not reported results by gender. Nicotine activates the brain's mesolimbic dopaminergic reward system and produces dependence, resulting in withdrawal symptoms with abrupt cessation. Nicotine has been implicated in the development of various diseases through its effects on the microvasculature and on the function of platelets, fibroblasts, red blood cells, and other blood components. In addition, cigarette smoke contains carbon monoxide and at least 60 other toxic substances that exert harmful effects in many human tissues through direct and indirect mechanisms. Seven of these compounds are known human carcinogens. Effects on Pregnancy:The biologic evidence that maternal smoking has a detrimental effect on the fetus includes, fetal hypoxia from increased carboxy-hemoglobin; reduced blood flow to the uterus, placenta, and fetus; and direct effects of nicotine and other compounds in tobacco smoke on the placenta and fetus. Health risks associated with smoking during pregnancy include intrauterine growth restriction, placenta previa, and abruptio placentae. Adverse pregnancy outcomes include premature rupture of membranes, low birth weights, and perinatal mortality. It is estimated that elimination of smoking during pregnancy would reduce infant deaths by 5% and reduce the incidence of singleton low-birth-weight infants by 10.4%. Successful smoking cessation before the third trimester eliminates much of the reduced birth weight caused by maternal smoking. Women who continue to smoke during pregnancy must achieve very low levels of tobacco use to see improvements in infant birth weight, and they must have birth weights similar to those of women who do not smoke (4). Effects on Newborns and Children:There is a strong association between smoking during pregnancy and sudden infant death syndrome (SIDS). Children born to mothers who smoke during pregnancy are at increased risk for asthma, susceptible to respiratory diseases, otitis media, infantile colic, and childhood obesity. Among children with established asthma, second-hand smoke exposure may cause additional episodes and increase its severity (5). The Millennium Development Goals (MDGs) & Tobacco Control:The rapid increase in tobacco consumption and its spread around the world represents a great concern to public health both globally and at the national level. Tobacco is the second major cause of death in the world and the fourth most common risk factor for disease worldwide. Among the eight MDGs, six are related to health, which shows how important the links are between good health and efforts to combat poverty and ensure sustainable development (6).
Intervention:Both cessation of tobacco use and prevention of relapse to smoking are key clinical intervention of smoking during pregnancy. Techniques for helping patients to stop smoking have included counseling, cognitive and behavioral therapy, hypnosis, acupuncture, and pharmacologic therapy. The provider also may refer the patient to a smoker's quit-line. Telephone quit-lines offer information, direct support, and ongoing counseling and have been very successful in helping pregnant smokers quit and remain smoke free. Although counseling and pregnancy-specific materials are effective cessation aids for many pregnant women, some women continue to smoke. Women who continue to smoke may benefit from screening for alcohol use and other drug use. Quitting smoking early in pregnancy yields the greatest benefits for the pregnant woman and fetus, quitting at any point can be beneficial. The benefits of cutting down are difficult to measure or verify. Approximately 60%-80% of women who quit smoking during pregnancy return to smoking within a year postpartum. Former smokers should be counseled in the third trimester and at the postpartum visit and subsequent gynecology visits concerning relapse to smoking. The use of nicotine replacement products or other pharmaceuticals for smoking cessation aids during pregnancy and lactation have not been sufficiently evaluated to determine their efficacy or safety. Nicotine gum, lozenges, patches, inhalers and special-dose antidepressants for the withdrawal symptoms, such as bupropion, should be considered for use during pregnancy and lactation only when non-pharmacologic treatments (eg, counseling) have failed. If the increased likelihood of smoking cessation, with its potential benefits, outweighs the unknown risk of nicotine replacement and potential concomitant smoking, nicotine replacement products or other pharmaceuticals may be considered (7). If the nicotine patch is used, it can be removed at night to reduce fetal nicotine exposure. Nicotine replacement therapy also may be considered during lactation. Optimally, smokers can be treated with these pharmaco-therapies before conception. World Health Organization Tobacco Free Initiative:The WHO Framework Convention of Tobacco Control (WHO FCTC) was developed in response to the current globalization of the tobacco epidemic. The spread of the tobacco epidemic is facilitated by a variety of complex factors with cross-border effects, including trade liberalization, foreign direct investment, and other activities such as global marketing, transnational tobacco advertising, promotion and sponsorship, and the international movement of contraband and counterfeit cigarettes. The WHO FCTC is an evidence-based treaty that reaffirms the right of all people to the highest standard of health. This is a landmark for the future of global public health and has major implications for WHO's health goals. On 21 May 2003, the 56th World Health Assembly unanimously adopted the WHO Framework Convention on Tobacco Control. The Convention was opened for signature, for period of one year, from 16 June 2003 to 22 June 2003 at WHO headquarters in Geneva and thereafter at United Nations Headquarters in New York, from 30 June 2003 to 29 June 2004. For further information please visit the website: http://tobacco.who.int Effects of Maternal Cigarette Smoking on Placental Volume and Vascularization:Although the profound effects of maternal smoking on birth size are well established, little is known about the underlying mechanisms constraining fetal growth. Morphologic studies indicate that smoke produces a direct effect on placental development with a decrease in its vascularization. However, Doppler studies of uterine and umbilical circulations have failed to validate this hypothesis. Recent advances in ultrasound permit 3-dimensional (3D) ultrasound to be combined with power Doppler. The resulting capacity makes it possible to quantify Doppler signals in a volume obtained by 3D scanning, thus allowing the operator to assess the entire placental circulation. The results of this study confirm the association between smoking and a significant reduction in birth weight. Smoking <10 cigarettes/day did not alter the 3D Doppler placental vascular indices under study. In mothers who smoked heavily, however, all these indices were significantly reduced, suggesting that a reduced placental vascularization was already present at 11+0 to 13+6 weeks of gestation (9). This study revealed a significant relationship between degree of placental vascularization and birth weight suggesting that smoking induces early reduction of placental angiogenesis, thereby influencing size at birth. In a cohort study with perspective data from 1996 to 2002 of 87,032 singleton pregnancies enrolled in the Danish National Birth Cohort for which information on nicotine replacement therapy use and smoking is available (8). The authors conducted a Cox regression analysis to estimate the hazard ratio and 95% confidence interval of stillbirth according to the status of use of nicotine replacement therapy, type of nicotine replacement therapy use, and a combination of nicotine therapy use and smoking. The outcome was stillbirth occurring after 20 weeks of gestation. A total of 495 pregnancies (5.7 per 1,000 births) ended in stillbirth; eight were among nicotine replacement therapy users (4.2 per 1,000 births). After adjustment for cofounders, women who used nicotine replacement therapy during pregnancy had hazard ratio of 0.57 (95% confidence interval, 0.28-1.16) for stillbirth compared with women who did not use nicotine replacement therapy. Smoking during pregnancy was associated with an increased risk of stillbirth (hazard ratio 1.46; 95% confidence interval, 1.17-1.82), whereas women who both smoked and used nicotine replacement had hazard ratio of 0.83 (95% confidence interval, 0.34-2) compared with non-smoking women who did not use nicotine replacement therapy. Although smoking has been demonstrated to be related to stillbirth in several studies, in this study the use of nicotine replacement therapy did not demonstrate an association with increased risk of stillbirth. The study was hampered by a relatively low number of nicotine replacement therapy users and a limited number of exposed stillbirths. Nevertheless, it does suggest that nicotine replacement therapy use in pregnancy does not impart a serious risk for stillbirth and this information is useful for obstetricians who wish to encourage their patients to substitute nicotine replacement therapy for smoking during pregnancy. Whereas the nicotine in this therapy is a toxin that may be injurious to a pregnancy, it probably is less likely to cause injury than the multiple toxins in cigarette smoking. An increased incidence of low-birth-weight infants have been ascribed to heavy cigarette smoking by pregnant women. This effect seems to be dose-related. Smoking also increases the risk of fetal death or damage in-utero. Smoking similarly increases the risk of abruptio placentae and placenta previa, each of which increases the fetal risk as well as the maternal risk of death or damage. Since there are many potentially hazardous substances in tobacco smoke, the particular one responsible for these adverse effects has not been identified. Pregnant women should be encouraged not to smoke. If quitting is too stressful, the patient should at least cut down on the number of cigarettes smoked per day. Many private and public insurers are changing policy to provide coverage for smoking cessation counseling for pregnant women. Promote hospital policies that support and provide smoking cessation services. The Project is funded by the WHEC Initiative for Global Health. |