Smoking marijuana could hurt fertility in women as well as men, according to a new research paper whose lead author says more investigation of the subject is needed.

The article, published Monday in the Canadian Medical Association Journal (CMAJ), found that smoking marijuana can contribute to delayed ovulation, reduced sperm counts and decreased odds of conception.

The paper cites an earlier study of 201 pot-smoking women, 29 of whom who had smoked at least once within three months experienced delayed ovulation by an average of 1.7 to 3.5 days.

Another cited study of 1,215 healthy men between 18 and 28 years old found that those who smoked marijuana more than once weekly within a three-month period had a 29% reduction in total sperm count.

What’s more, Lani J. Burkman, a founder of an e-fertility diagnostics lab who led a separate study involving college men, told WebMD.com that the sperm from marijuana-smoking men became hyperactivated, or swam too fast and too early.

So instead of fertility, the activity lead to burnout, said Dr. Burkman, chief technology officer of LifeCell Dx.

But the few human studies on marijuana and fertility are “small, nonrandomized and mainly retrospective,” notes the CMAJ research paper, written by Sara Ilnitsky and Stan Van Uum.

National survey data suggests that smoking less than a ounce of marijuana a month does not affect pregnancy. But for couples who struggle with infertility, the changes in ovulation and sperm count associated with smoking marijuana could add to difficulties in becoming pregnant.

The body’s endocannabinoid system regulates several aspects such as appetite, mood and pain sensation as well as cognitive functions such as memory. THC, psychoactive ingredient in marijuana, activates the system’s receptors, which are located in the brain, nervous system and reproductive organs.

“So if you are adding external cannabinoid in the form of THC, there’s a possibility that you could be disrupting these very finely tuned balances within the reproductive organs,” said Dr. Ilnitsky, a obstetrician/gynecologist who specializes in fertility.

Ten states in the U.S., the District and Canada have legalized recreational marijuana. In May, the Illinois state legislature passed a bill legalizing the sale and possession of marijuana. The bill now awaits signature from Gov. J.B. Pritzker.

“As it’s becoming more and more legal, [marijuana] uniquely positions us to do this research because it’s more accessible,” Dr. Ilnitsky said. “People are also more willing to admit to using it.”

“We need more research, and we need more people looking at this to try and find out exactly what’s going on and how significant the effect is,” she added.

Dr. Ilnitsky and Dr. Van Uum, who specializes in endocrinology, said the findings about fertility and marijuana should be interpreted with caution.