BACKGROUND AND OBJECTIVES: Nicotine replacement therapy (NRT) is now being used as a smoking cessation aid during pregnancy, although little is known about fetal safety. We assessed the relationship between early pregnancy exposure to NRT or smoking with major congenital anomalies (MCA) in offspring. METHODS: We studied 192,498 children born in the United Kingdom between 2001 and 2012 with linked mother-child primary care records. The absolute risks of MCAs in the NRT group (women prescribed NRT during the first trimester or 1 month before conception [and therefore likely consumed during the first trimester]) and odds ratios (ORs) and 99% confidence intervals (CIs) were compared with those of women who smoked during pregnancy and with a control group (women who neither smoked nor were prescribed NRT); logistic regression models adjusted for maternal morbidities that increase MCA risk were used for analysis. RESULTS: MCA prevalence was 288 per 10,000 live births (5535 children with >/= 1 MCA). Maternal morbidities were most common in the NRT group (35%) followed by smokers (27%) and the control group (20%). Compared with the control group, adjusted ORs for MCAs in the NRT group and smokers were 1.12 (99% CI: 0.84-1.48) and 1.05 (99% CI: 0.89-1.23), respectively. The OR comparing the NRT group directly with smokers was 1.07 (99% CI: 0.78-1.47). There were no statistically significant associations between maternal NRT and system-specific anomalies except for respiratory anomalies (OR: 4.65 [99% CI: 1.76-12.25]; absolute risk difference: 3 per 1000 births), which was based on 10 exposed cases. CONCLUSIONS: For most system-specific MCAs, we found no statistically significant increased risks associated with maternal NRT prescribed during pregnancy, except for respiratory anomalies. Although this study is the largest published to date, NRT use in pregnancy remains rare; thus, the statistical power was limited. Higher morbidities in those women prescribed NRT may also be an explanatory factor. Nevertheless, absolute MCA risks were similar between women who smoked and those prescribed NRT during pregnancy.
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