This factsheet has been written for members of the public by the UK Teratology Information Service (UKTIS). UKTIS is a not-for-profit organisation funded by Public Health England on behalf of UK Health Departments. UKTIS has been providing scientific information to health care providers since 1983 on the effects that medicines, recreational drugs and chemicals may have on the developing baby during pregnancy.

There is evidence to suggest that using cannabis during pregnancy may increase the chance of having a preterm and/or low birth weight baby and could affect a child’s long-term learning and behaviour. Cannabis is often mixed with tobacco for smoking, and smoking tobacco during pregnancy has been strongly linked to certain pregnancy problems (please see the smoking bump for further details).