ABC News reports….

When men smoke marijuana once a week or more, their partners are twice as likely to experience a miscarriage when pregnant, according to Boston University researchers who examined over 1,400 couples before they got pregnant.

The researches asked the couples about marijuana usage over the past two months and then followed them as they got pregnant and, in some cases, miscarried.

The majority of men in the study did not smoke marijuana, with only 8% smoking once a week or more. Nearly 18% of the couples in the study reported a miscarriage.

Smoking, but less frequently than once a week, did not have an association with miscarriage rate, according to the research.

One reason for the increased risk of miscarriage with male marijuana use, according to researchers, is that smoking marijuana may negatively affect sperm quality and the change in sperm quality may drive the increased occurrence of miscarriage.

The research is being presented Monday at the American Society for Reproductive Medicine Congress & Expo in Philadelphia.

Full report: https://abcnews.go.com/GMA/Wellness/mens-marijuana-increases-miscarriage-risk-women-research-finds/story?id=66257753