Other studies have shown that frequent marijuana use lowers sperm count and mobility of sperms in males. Men who are frequent cannabis users are twice as likely to see their partner’s pregnancy end in a miscarriage, according to new data-driven research. A new study suggests men intending to conceive a child with their partner should reconsider their marijuana use. When examining miscarriages related to regular marijuana use, researchers found they typically happened within eight weeks of conception. When examining miscarriages related to regular marijuana use, researchers found that miscarriages typically happened within eight weeks of conception, U.S. News & World Report first reported.