Snus users had high levels of nicotine, cotinine and 3-hydroxycotinine in their breastmilk, and the clearance was slower than in smoking mothers.

AIM: Using snus, an oral moist tobacco, has increased among pregnant women in Sweden, the only European Union country where sales are legal. This study evaluated whether snus generated similar concentrations of nicotine and its metabolites in breastmilk to cigarette smoking.
METHODS: We analysed 49 breastmilk samples from 33 nursing mother - 13 snus users, six cigarette smokers and 14 controls - for concentrations of nicotine, cotinine and 3-hydroxycotinine. The mothers were recruited at antenatal clinics in Sweden from 2007 to 2012.
RESULTS: The median nicotine concentration in breastmilk of the snus users was 38.7 ng/mL (0-137) versus 24.0 ng/mL (0-56) in smokers, with median cotinine levels of 327.6 ng/mL (37-958) versus 164.4 ng/mL and median 3-hydroxycotinine levels of 202.7 ng/mL (28-452) versus 112.4 (0-231), respectively. Nicotine was still detected in the breastmilk of eight of the 13 snus users after abstaining from tobacco for a median duration of 11 hours (0.6-12.5), while the breastmilk of the smokers was nicotine-free after four hours' abstinence.
CONCLUSION: Snus users had high levels of nicotine and metabolites in their breastmilk and nicotine was found even after 12.5 hours of abstinence. ©2018 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.