Maternal Smoking, Nicotine Replacement Therapy in Pregnancy and Stillbirth: A Population-based Study using United Kingdom Primary Care Data

INTRODUCTION:  Maternal smoking during pregnancy has been associated with stillbirth in a dose-dependent manner. No conclusions however have yet been established about the association between the use of NRT during pregnancy and the risk of stillbirth. Therefore, we aimed to assess the relationship between smoking and NRT use during pregnancy and stillbirth.

METHODS:  We accessed data on all pregnancies in women of reproductive age between 2001-2012 using a mother-child linked dataset of primary care records from across the UK. Mothers’ smoking status and NRT use during pregnancy were identified and the risk of stillbirth was calculated in pregnancies of mothers who smoked or used NRT any time during pregnancy compared to non-smoking mothers using logistic regression, adjusting for maternal characteristics and morbidities.

RESULTS: Out of a total of 388,142 pregnancies, 1,519 (4/1000 births) ended in stillbirth. During pregnancy 17% of mothers were classified as smokers and 1.4% as NRT users. Compared with non-smokers the adjusted odds ratios (OR) for stillbirth in pregnancies of women classified as smokers or in those prescribed NRT when pregnant were 1.25 (99% confidence interval (CI) 1.04-1.51) and 1.39 (99% CI 0.83-2.31) respectively. 

CONCLUSIONS:  This work reiterates that maternal smoking during pregnancy increases the risk of stillbirth and also suggests that there is no significant association between NRT use during pregnancy and stillbirth.