Data consistently support the negative impact of tobacco use in pregnancy with respect to pregnancy outcome, and the benefits of discontinuation or reduction as early as possible.
Recent analyses by investigators at the National Center on Birth Defects and Developmental Disabilities at the Centers for Disease Control and Prevention suggest that more than 6% of oral clefts, or 430 affected infants per year in the United States, could be prevented annually if women can discontinue tobacco use prior to conception (Birth Defects Res A Clin Mol Teratol. 2014 Nov;100[11]:822-5). Similarly, preconception smoking cessation could prevent the 1.4% of nonsyndromic congenital heart defects that are attributable to maternal smoking in the first trimester (J Pediatr. 2015 Apr;166[4]:978-984.e2).
With respect to the risk for adverse outcomes beyond the first trimester, recent data also show clearly that the trimester of discontinuation is related to intrauterine growth restriction in a dose-response fashion (Obstet Gynecol. 2015 Jun;125[6]:1452-9).
Dr. Christina D. Chambers
In a recent population-based retrospective cohort study of 927,424 singleton births 2006-2012 in Ohio, the adjusted relative risk of infant birth weight less than the 5th percentile for those women who discontinued smoking after the first trimester compared with nonsmokers was 1.25 (95% confidence interval, 1.17-1.33); for those who discontinued after the second trimester the relative risk was 1.83 (95% CI, 1.68-1.99); and for those who smoked throughout pregnancy the relative risk was 2.44 (95% CI, 2.37-2.51).
Given the compelling reasons to encourage women to stop smoking or at least to reduce harm during pregnancy, options for assistance with smoking cessation are of high interest. Beyond simple screening and advice to quit, cognitive behavioral therapy has been shown to provide some benefit. The addition of pharmacologic treatment with nicotine replacement therapy (NRT) has been studied in six randomized clinical trials (RCTs) conducted in pregnant women, four of which compared NRT plus advice/behavioral support to placebo plus advice/behavioral support, and two of which compared NRT plus advice/behavioral support to advice/behavioral support alone.
In a recent Cochrane systematic review of these studies, no statistically significant evidence of effectiveness was demonstrated for NRT versus placebo/control in a pooled sample of 1,745 pregnant patients (risk ratio, 1.33, 95% CI, 0.93-1.91). However, there was high heterogeneity in the dose of NRT and the delivery method (e.g., gum, patch) across studies, and poor adherence to the NRT treatment in all trials (Cochrane Database Syst Rev. 2012 Sep 12;9:CD010078).
With respect to safety, in the same Cochrane review there were no statistically significant differences in rates of miscarriage, stillbirth, premature birth, birth weight, low birth weight, admissions to neonatal intensive care, or neonatal death between NRT and control groups. However, small sample sizes and adherence issues across these trials hampered the interpretability of these data.
One relatively large claims database study from the United Kingdom, which was published recently, examined major congenital anomalies following prescription of NRT. The investigators found no increased risks for most major defects following NRT prescription; the only significant association was with respiratory defects (Pediatrics. 2015 May;135[5]:859-67).
The general thinking has been that for a woman who is unable to quit smoking without pharmacological assistance, NRT that delivers nicotine alone to the developing fetus may be a better option than exposure to the multiple toxins that are contained in tobacco smoke. However, there is considerable controversy over the potential adverse neurotoxic effects of nicotine itself and long-term neurodevelopmental studies on children prenatally exposed to NRT are lacking.
Catherine Harrell/Frontline Medical News
Other options include bupropion and varenicline, neither of which have been studied in RCTs in pregnancy. Bupropion has been evaluated in a small controlled cohort study, a claims database study (n = 1,236 first-trimester exposed), and two case-control studies. None of these studies was focused on use of bupropion exclusively for smoking cessation, but rather for the more common indication of maternal depression. The first two studies suggested no increased risks for adverse pregnancy outcomes compared to women the same underlying conditions; the case control studies suggested small increased risks for heart defects but not the same ones in both studies (Expert Opin Drug Saf. 2014 Dec;13[12]:1721-31). The limited data on varenicline are too sparse to make any inferences.
Another possible alternative that has been gaining in popularity are e-cigarettes or related vapor products, which are touted to have advantages with respect to harm reduction, primarily because of possible improved adherence due to their similarity to conventional smoking. However, there is large variability in the amount of nicotine in the vapor of various e-cigarette brands, and some have suggested that e-cigarette users engage in longer puff duration than do those who smoke conventional cigarettes. To my knowledge, there are no controlled studies of e-cigarette use in pregnancy, but the concerns previously raised regarding nicotine exposure in any form likely apply to this delivery method (Birth Defects Res A Clin Mol Teratol. 2015 Mar;103[3]:186-95).