There is little evidence to show a directly harmful effect of cannabis in pregnancy. However, cannabinoids consistently amplify the toxic effects of nicotine and alcohol on the fetus. Preclinical research suggests one possible reason: activating the CB2 receptor with anandamide can decrease the expression of a transporter gene in the placenta. This gene encodes a protein which pumps a variety of chemicals out of the placenta, so its inhibition allows toxins to accumulate. It is also common in cancers where it protects the cancer from chemo. Other studies have suggested that cannabinoids may synergize with chemotherapies by interacting with this same chemical transporter. Previous research has highlighted that anandamide, in particular, may worsen fetal alcohol syndrome.