"This study was designed to determine how therapeutic users of cannabis rate its effectiveness as an anti-emetic, and particularly as a treatment for nausea and vomiting of pregnancy. In general (not specific to pregnancy), the vast majority of our respondents considered cannabis to be extremely effective or effective as a therapy for nausea (93%) and vomiting (75%), and as an appetite stimulant (95%). In the context of pregnancy, cannabis was rated as extremely effective or effective by 92% of the respondents who had used it as a therapy for nausea and vomiting (morning sickness)."

Source

Westfall, Rachel E.; Janssen, Patricia A.; Lucas, Philippe; and Capler, Rielle, "Survey of medicinal cannabis use among childbearing women: Patterns of its use in pregnancy and retroactive self-assessment of its efficacy against ‘morning sickness'," Contemporary Therapies in Clinical Practice (United Kingdom: November 2009) Vol. 15, Issue 4, p. 32.
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