The rate of cigarette smoking during pregnancy has declined to about 11%, but the prevalence is higher in younger (under 20 years) and older (over 35 years) women.
Smoking is a significant cause of embryonic, fetal, neonatal, infantile, and adolescent toxicity that includes growth restriction, a small increased risk for some birth defects, functional-neurobehavioral deficits, and death. In the 8th edition of “Drugs in Pregnancy and Lactation,” smoking is cited as a major cause of premature birth, placental abruption, placenta previa, and premature rupture of the membranes (Philadelphia: Lippincott Williams & Wilkins, 2008). Because of the dose-effect relationship between smoking and these toxicities, pregnant women should try to stop, or at least reduce, smoking.
The primary intervention strategy is nonpharmacologic: counseling, acupuncture, and hypnotherapy. A 2005 American College of Obstetricians and Gynecologists Committee Opinion detailed an intervention known as the 5 A's: Ask, Advise, Assess, Assist, and Arrange (Obstet. Gynecol. 2005;106:883–8), which also provided resources for smoking cessation. The few studies conducted with acupuncture and hypnotherapy have not clearly shown these therapies to be more effective than placebo; larger and better-designed studies are warranted (Clin. Obstet. Gynecol. 2008;51:419–35).
Pharmacologic therapy may be required if counseling is not successful. Such interventions include varenicline (Chantix); nicotine replacement therapy (NRT) with patches, gum, lozenges, inhalers, and nasal sprays); antidepressants, such as bupropion (Zyban, Wellbutrin); and nonspecific therapies.
The Food and Drug Administration approved varenicline for smoking cessation in 2006. Its mechanism is unique in that it prevents nicotine from binding to nicotinic acetylcholine receptors. Reproduction studies in animals are reassuring, but there are no human pregnancy data. Nevertheless, if a woman requires this therapy, the risk-to-benefit ratio appears to favor use of the drug.
The use of NRT in pregnancy is controversial. Nicotine is the primary chemical derived from smoking and it is a toxin, and since smoking is known to increase the risk of developmental toxicity, the same could occur with NRT. Although nicotine patches produce nicotine serum levels that are similar to smoking, they prevent exposure to other toxins, such as carbon monoxide, cyanide, dioxin, cadmium, thiosulfate, and the more than 3,000 other compounds identified in cigarette smoke. Removing the patch at night before going to sleep will reduce nicotine serum levels for part of the day. Nicotine gum, lozenges, inhaler, and nasal spray produce lower maternal nicotine serum levels but they may cause adverse effects such as poor taste and throat and nasal irritation and reduce compliance.
One study found a nonsignificant increase overall in birth defects in babies of women using NRT (Obstet. Gynecol. 2006;107:51–7). But there were significant increases in cleft lip and defects of the digestive tract and cardiovascular system. The data suggested an increased risk of defects but the authors could not prove or exclude causality.
Bupropion is approved by the FDA for smoking cessation and seems to be effective in reducing withdrawal, weight gain, and cravings. Adverse effects, such as insomnia, dry mouth, and an increased risk of seizures, can be problems, but the drug is more effective than NRT and does not expose the mother or the embryo-fetus to nicotine. The bupropion birth defect registry (now closed) collected data from 1997 to late 2007. It reviewed 1,005 prospective pregnancy outcomes and was able to exclude a major teratogenic effect. However, it was not designed to exclude an increase in the risk of specific defects.
Nonspecific therapies include the antihypertensive/central analgesic clonidine, narcotic antagonists naloxone and naltrexone, and melatonin. They've not been effective against smoking. Melatonin has not been studied in pregnancy or lactation and should be avoided.
Smoking decreases the duration of breastfeeding and exposes the nursing infant to nicotine and other toxins. If a mother can't stop smoking, she should at least not smoke around the infant or while nursing. The risks of using NRT during lactation are unclear because they have not been defined. Varenicline is probably excreted into milk and could cause adverse effects in the infant. Bupropion is excreted into milk and, in the case of one infant exposed via breast milk, no adverse effects were observed.
Counseling is the preferred treatment for smoking cessation. Bupropion would be my first choice for pharmacologic therapy, followed by varenicline, then NRT (avoid NRT in the first trimester.