(Portland, OR) -- Pregnant women using cannabis could impact the DNA of their fetus. Research from Oregon Health & Science University found in pregnant monkeys, THC, the main psychoactive ingredient in marijuana, can cause changes to DNA that's linked to autism and attention deficit hyperactivity disorder. Cannabis is one of the most commonly used drugs, and the perception is it's safe to use. Some women use it during the first trimester to reduce symptoms of morning sickness. Researchers hope the study improves discussions between medical providers and patients.