“If you’re a cannabis smoker and you’re trying to have a baby … stop.”
This advice comes from Dr, Allan Pacey, senior lecturer in andrology at the University of Sheffield in the United Kingdom and lead author of a new study that suggests using marijuana could increase a man’s risk of fertility problems.
The study, published in the journal Human Reproduction, looked at how a man’s lifestyle affects his sperm morphology: the size and shape of sperm. Researchers collected data from 1,970 men who provided semen as part of a fertility assessment.
All of the lifestyle information was self-reported, and researchers made no attempt to confirm accuracy.
Of those men, 318 produced abnormal sperm, where less than 4% of it was the correct size and shape (as defined by the World Health Organization). The remaining men’s sperm had a higher percentage at a “normal” size and shape.
The study found that men who had less than 4% normal sperm were typically under 30 years old, had used marijuana within three months of giving their sample and were twice as likely to have provided their sample during the summer.
Any of those factors could have influenced sperm morphology, but Pacey said “the only thing we found that was a risk that a man can do something about was cannabis.”