E-cigarette minimum legal sale age laws and traditional cigarette use among rural pregnant teenagers.

Teenagers under 18 could legally purchase e-cigarettes until states passed minimum legal sale age laws. These laws may have curtailed teenagers' use of e-cigarettes for smoking cessation. We investigate the effect of e-cigarette minimum legal sale age laws on prenatal cigarette smoking and birth outcomes for underage rural teenagers using data on all births from 2010 to 2016 from 32 states. We find that the laws increased prenatal smoking by 0.6 percentage points (pp) overall. These effects were concentrated in prepregnancy smokers, with no effect on prepregnancy non-smokers. These results suggest that the laws reduced cigarette smoking cessation during pregnancy rather than causing new cigarette smoking initiation. Our results may indicate an unmet need for assistance with smoking cessation among pregnant teenagers.