Use of nicotine replacement therapy during pregnancy and stillbirth:: a cohort study

Objective The objective of this study was to examine whether the use of nicotine replacement therapy (NRT) during pregnancy increases the risk of stillbirth. Design Cohort study with prospective data. Setting Denmark 1996-2002. Population A total of 87 032 singleton pregnancies enrolled in the Danish National Birth Cohort for which information on NRT use as well as smoking was available. Methods Outcome of pregnancy was identified by register linkage, with < 1% loss to follow up. We conducted Cox regression analyses to estimate the hazard ratio (HR) and 95% CI of stillbirth according to the use of NRT, type of NRT use and a combination of NRT use and smoking. Main outcome measures Stillbirth, defined as delivery of a dead fetus after 20 completed weeks of gestation. Results A total of 495 pregnancies (5.7 in 1000 births) ended in stillbirth, 8 of which were among NRT users (4.2 in 1000 births). After adjustment for confounders, women who used NRT during pregnancy had a HR of 0.57 (95% CI 0.28-1.16) for stillbirth compared with those who did not use NRT. Smoking during pregnancy was associated with an increased risk of stillbirth (HR 1.46, 95% CI 1.17-1.82), while women who both smoked and used NRT had a HR of 0.83 (95% CI 0.34-2.00) compared with nonsmoking women who did not use NRT. Conclusion Our study does not indicate that use of NRT during pregnancy increases the risk of stillbirth.