No Clear Link Between Smoking Cessation Drugs during pregnancy and Birth Defects: JAMA
Researchers have discovered in a study published in JAMA Internal Medicine that exposure to typical smoking cessation drugs in early pregnancy is not likely to substantially raise the risk of major congenital malformations (MCMs) in infants. This study indicates that prenatal nicotine replacement therapy (NRT), varenicline, or bupropion exposure does not seem to be linked with a distinct increase in total birth defects when compared to ongoing smoking in the first trimester. These findings provide some reassurance about the fetal safety of pharmacologic quitting aids during pregnancy, although certain specific risks might remain to be investigated. The study was conducted by Duong T. and fellow researchers.
Even though NRT, varenicline, and bupropion are effective and commonly used drugs for assisting quitting smoking, their pregnancy safety has been unclear. Pregnancy smoking can lead to a broad spectrum of negative outcomes, such as birth defects. Investigators did a large retrospective cohort study based on the data from four nations—Australia (New South Wales), New Zealand, Norway, and Sweden—on births between 2001 and 2020. The purpose was to evaluate if prenatal use of the drugs raises the risk of major congenital malformations.
The group comprised 391,474 infants to 267,522 women who smoked in the first trimester or had a smoking cessation drug in the 90 days prior to conception or in the first trimester. The analysis found 9325 infants exposed to NRT, 3031 to varenicline, and 1042 to bupropion. By means of prescription records, hospital data, and vital statistics, researchers conducted propensity score matching (1:10) and combined data in meta-analyses to compare outcomes between exposed and unexposed infants. The unexposed group included infants born to women who smoked but were not prescribed any pharmacotherapy.
Key Findings
• NRT exposure was not linked to a significant increase in total MCMs (37.6 vs 34.4 per 1000 live births; adjusted relative risk [aRR], 1.10; 95% CI, 0.98–1.22).
• Varenicline exposure likewise had no significant increase in total MCMs (32.7 vs 36.6 per 1000 live births; aRR, 0.90; 95% CI, 0.73–1.10).
• Bupropion exposure had no overall increase in birth defects (35.5 vs 38.8 per 1000 live births; aRR, 0.93; 95% CI, 0.67–1.29).
• NRT was associated with an increased risk of malformations of digestive organs (3.8 vs 2.5 per 1000 live births; aRR, 1.53; 95% CI, 1.05–2.23), although this did not reach statistical significance after adjusting for multiple comparisons (P = .41).
• Varenicline was linked to a higher risk of kidney and urinary tract malformations (11.5 vs 4.2 per 1000 live births; aRR, 2.75; 95% CI, 1.42–5.34), although this also failed significance after adjustment for multiple comparisons (P = .09).
• Information regarding bupropion was too sparse to analyze individual malformation subtypes.
The study authors found no definite evidence that prenatal exposure to NRT or varenicline is linked with a higher overall risk of major congenital malformations than continued smoking during early pregnancy. These findings provide evidence for the potential safety of smoking cessation pharmacotherapies during pregnancy, although additional study is required for uncommon outcomes and for bupropion owing to sparse data.
Reference:
Tran DT, Cohen JM, Donald S, et al. Risk of Major Congenital Malformations Following Prenatal Exposure to Smoking Cessation Medicines. JAMA Intern Med. Published online March 31, 2025. doi:10.1001/jamainternmed.2025.0290
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