The result came as a surprise to Harvard University scientists measuring the sperm counts of more than 600 men from couples attending a fertility clinic.
The team assessed data on 622 men, with an average age of 36, who visited Massachusetts General Hospital Fertility Center between 2000 and 2017.
It found that men who reported ever using cannabis actually had higher sperm counts on average than men who claimed to have never touched the stuff.
"An equally important limitation is the fact that most of the data were collected while cannabis was illegal in MA, so it is hard to know to what extent men may have under-reported use of cannabis because of social stigma or potential consequences related to insurance coverage for infertility services", he said.
Analysis of the sperm count indicated those who reported to have smoked marijuana had a sperm count of 62.7 million sperms per millilitre as compared to those who had never smoked with an average of 45.4 million/ml.
There was also no significant difference in sperm concentrations between current and former marijuana smokers, and greater use of marijuana among marijuana smokers was associated with higher testosterone levels in the blood. And while 12 per cent of non-tokers had a low sperm count (15 million sperm per milliliter of semen or less), the same was true for only 5 per cent of cannabis users.
Chavarro warned that the findings don't necessarily mean that smoking pot increases the chances of making a baby.
Study author Dr Jorge Chavarro, Associate Professor of Nutrition and Epidemiology at Harvard T.H. Chan School of Public Health, said the drug requires more research.
"Our results need to be interpreted with caution and they highlight the need to further study the health effects of marijuana use", he added.
And yet, the study still found that men who said they used marijuana at least a year ago had higher sperm counts than men who used it more recently. But many of these studies have only involved animals or focused on a small group of people (including the one last December). Participants were asked to fill in questionnaires detailing their history of cannabis use.
Other experts in the field have questioned how robust the association is. For men who smoke marijuana and are planning on having children, the advice keeps getting more confusing.
Feiby Nassan, lead author of the study and a postdoctoral research fellow at Harvard Chan School, told Newsweek: "Because the endocannabinoid receptors (the ones responsive to marijuana) are found in many places in the body especially the reproductive system, we need to understand their role on our health, especially with increasing their legalization".
Among men who had ever smoked marijuana, those who used it more often had higher testosterone levels than those who used it less often.
Writing in the journal Human Reproduction, the scientists said it was possible that low level exposure to cannabis might benefit sperm production in some way. Another reason, according to the researchers, is that men may be more likely to engage in "risk-seeing activities", like smoking marijuana, if they have higher testosterone concentrations- something that aids in fertility.