Changes in the rate of nicotine metabolism across pregnancy: A longitudinal study
Author(s)
Katharine Bowker, Sue Cooper and Sarah Lewis
Presenter(s)
Katherine Bowker PhD Student, Division of Primary Care, University of Nottingham
Abstract
Nicotine replacement therapy is effective outside pregnancy, but there is no evidence it is effective in pregnancy. Nicotine metabolism increases in late pregnancy, so the standard dose of NRT may not be enough to alleviate nicotine cravings. However it is unknown when changes occur, so this study investigated longitudinal variations in nicotine metabolism across pregnancy. Saliva samples from 101 pregnant smokers at 8-14, 18-22 and 32-36 weeks gestation, 4 and 12 weeks postnatally were collected to measure the nicotine metabolite ratio (NMR), using the ratio of cotinine to its primary metabolite trans-3’-hydroxycotinine. Multi-level modelling was used to detect any overall difference in NMR between time points.
Paired t-tests compared nicotine metabolism at 12 weeks postpartum with samples obtained during pregnancy and 4 weeks postpartum. We found NMR changed over time (p=0.0006). Compared to 12 weeks postpartum, NMR was 15% higher at 8-14 weeks (95% CI 1% to 26%, p=0.034), 26% higher at 18-22 weeks (95% CI 12% to 38%, p=0.001) and 23% higher at 32-36 weeks (95% CI 9% to 35%, p=0.003).
There was no difference at 4 weeks postpartum. We found an increased NMR was established in early pregnancy, which then decreased significantly in the postpartum.
Source of funding: This research is funded by the National Institute for Health Research (NIHR) School for Primary Care Research and the School of Medicine at the University of Nottingham.
Declaration of interest: Katharine Bowker, Sue Cooper and Sarah Lewis are members of the NIHR School for Primary Care Research. And are members of the UK Centre for Tobacco and Alcohol Studies (http://www.ukctas.ac.uk)
