Longitudinal Influence of Pregnancy on Nicotine Metabolic Pathways

Nicotine metabolism increases in pregnancy, which may contribute to the difficulties that pregnant women have in quitting smoking. We aimed to determine the extent and timing of changes in nicotine metabolic pathways, including C-oxidation, N-glucuronidation, and the pregnancy-induced influences on the activity of enzymes mediating these pathways (CYP2A6 and UGT2B10, respectively). Current smoking pregnant women ( n = 47) provided a urine sample during early pregnancy (12.5 weeks), late pregnancy (28.9 weeks), and 6 months postpartum. Concentrations of urinary nicotine and metabolites were analyzed using liquid chromatography tandem mass spectrometry and compared using general linear repeated measures analyses. Nicotine C-oxidation was 1.07-fold ( P = 0.12) and 1.11-fold ( P P = 0.06) and 1.67-fold ( P = 0.003) higher at early and late pregnancy, respectively, compared with postpartum. The CYP2A6 phenotype ratio (total 3′-hydroxycotinine/cotinine) was significantly higher at early and late pregnancy compared with postpartum (all P P P = 0.07 and P P