Smoking in pregnancy is the leading preventable cause of morbidity and death among women and infants. Adverse pregnancy and birth outcomes associated with smoking include placental abruption, miscarriage, prematurity, low birth weight, congenital abnormalities and neonatal or sudden infant death. 

The prevalence of smoking during pregnancy is 13-25% in high-income countries and is increasing rapidly in low-income and middle-income countries. Cessation of smoking during pregnancy is important for maternal and foetal health.

A meta-analysis of trials has shown that behavioural support for smoking cessation helps pregnant women to stop smoking, which improves birth outcomes. However, there is considerable uncertainty about whether or not medications that have been shown to improve cessation rates among non-pregnant women are also effective during pregnancy. 

Concerns regarding potential teratogenicity have prevented clinical trials of varenicline and bupropion. Such concerns are less pressing with nicotine-replacement therapy, because this therapy contains only nicotine, whereas tobacco smoke contains this and many other toxins.

There is a general consensus that nicotine-replacement therapy is probably less harmful than smoking, and its use in pregnancy is recommended by several sets of guidelines for smoking cessation in pregnancy. Yet good evidence to support these recommendations is lacking. 

To date, individual clinical trials of nicotine-replacement therapy in pregnancy have been too small to definitively assess if it is effective or safe in this context, and the pooled risk-ratio for cessation in later pregnancy obtained through meta-analysis of these studies is inconclusive (risk-ratio, 1.63; 95% confidence interval [CI], 0.85 to 3.14)

In a UK-based study¹, participants were recruited from seven hospitals in England who were 16-50 years of age with pregnancies of 12-24 weeks’ gestation and who smoked five or more cigarettes per day. Participants received behavioural cessation support and were randomly assigned to eight weeks of treatment with active nicotine patches (15mg per 16 hours) or matched placebo patches. 

The primary outcome was abstinence from the date of smoking cessation until delivery, as validated by measurement of exhaled carbon monoxide or salivary cotinine. Safety was assessed by monitoring for adverse pregnancy and birth outcomes.

Of 1,050 participants, 521 were randomly assigned to nicotine-replacement therapy and 529 to placebo. There was no significant difference in the rate of abstinence from the quit date until delivery between the nicotine-replacement and placebo groups (9.4% and 7.6%, respectively; unadjusted odds ratio with nicotine-replacement therapy, 1.26; 95% confidence interval, 0.82 to 1.96), although the rate was higher at one month in the nicotine-replacement group than in the placebo group (21.3% versus 11.7%). 

Compliance was low; only 7.2% of women assigned to nicotine-replacement therapy and 2.8% assigned to placebo used patches for more than one month. Rates of adverse pregnancy and birth outcomes were similar in the two groups.

Adding a nicotine patch (15mg per 16 hours) to behavioural cessation support for women who smoked during pregnancy did not significantly increase the rate of abstinence from smoking until delivery or the risk of adverse pregnancy or birth outcomes. However, low compliance rates substantially limited the assessment of safety.

Reference

1. Coleman T, Cooper S, Thornton JT et al, N Engl J Med 2012; 366: 808-818