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HighlightsContingency management (CM) reduces other drug use in opiate addiction treatment.Meta-analyses did not find evidence of effectiveness for non-prescribed opiate use.CM is effective for cocaine, tobacco, opiates + cocaine, tobacco, polysubstance use.Evidence is lacking for long-term effects.

Introduction Smoking in pregnancy increases the risk of negative health outcomes. Vaping can be effective for smoking cessation in non-pregnant populations. We conducted a systematic review of vaping in pregnancy, covering prevalence, patterns of use, reasons for use, smoking cessation and health effects. Methods Five academic databases were searched on 17 February 2020. Studies reporting prevalence, patterns, reasons, cessation or health effects of vaping in pregnancy were included; animal and in-vitro studies were excluded. A narrative review was used, with risk of bias assessed using Hoy and colleague’s tool, the Newcastle-Ottawa scale and the Consolidated Criteria for reporting Qualitative Research. Results Twenty-three studies were identified: 11 survey, seven qualitative, three cohort and two secondary analyses of RCTs. Prevalence of vaping in pregnancy (four studies) was between 1.2% and 7.0% overall, and <1% among non-smokers. Twelve studies reported patterns of use, but findings were inconsistent. Twelve of fourteen studies asking why pregnant women vaped reported that most vaped to reduce or quit smoking. Mixed findings were reported from six studies on smoking cessation. Of three studies with health-related outcomes, two were underpowered and one reported similar birthweights for babies born to non-smokers and women who vaped, with both higher (P<.0001) than the birthweight of babies born to smokers. Conclusions There were insufficient data to draw conclusions about prevalence, patterns and effects of vaping in pregnancy on smoking cessation. The limited literature suggests that vaping in pregnancy has little or no effect on birthweight.