On October 17, 2018, Canada legalized marijuana.  Sounds like the perfect time to look into the research on whether marijuana use can affect fertility!

What impact does marijuana have on fertility rates?  Can marijuana use affect a pregnancy?  What happens to sperm counts for men who smoke marijuana?  All these questions and much more will be answered below!


General Effects of Marijuana on Fertility

Many reports on how cannabis affects fertility tend to be mixed and speculative. However, there have been some intensive and comprehensive studies carried out to measure these effects.

The following are just a few of the general ways marijuana may impact fertility and pregnancy:

  • Marijuana appears to reduce the frequency of ovulation

  • Marijuana can negatively impact the GnRH (important sex hormones)

  • Marijuana disrupts the endocannabinoid system (more on this below)

  • THC (an active component of marijuana) can impact pregnancy by promoting:  reduced baby growth, premature labour and low birth weight

  • Marijuana can have negative effects on sperm parameters

Impact of Marijuana on Female Fertility

Far less research has been done on the effects of cannabis on female fertility than male fertility…particularly when it comes to fertility and pregnancy (probably a good thing).

The vast majority of health care practitioners recommend avoiding the use of marijuana for women who are trying to conceive, are already pregnant or in the breast-feeding stage.

Even though studies on female fertility and the effects of marijuana are rare, there are a few available to examine this scenario a little more closely.

Marijuana and Anovulation

Anovulation occurs when the ovaries cease to produce a mature egg for release during the menstrual cycle.

Obviously, this is a condition which can affect ones fertility. If no egg is being released, conception is certainly more difficult.

A study done on 201 women indicated that women who used marijuana had longer follicular phases. The length of the follicular phase increased as the marijuana use escalated.  This effect was also demonstrated with work on rhesus monkeys.

Marijuana Affects GnRH

Gonadotropin-Releasing Hormone, or GnRH, is a hormone that is produced in the hypothalamus area of the brain.

GnRH is responsible for the release of two other hormones:

  • FSH – Follicle Stimulating Hormone
  • LH – Luteinizing Hormone

These hormones are both directly involved in the ovulation process. An imbalance in these hormones can lead to infertility.

Marijuana use is thought to decrease GnRH production, leading to a reduction in estrogen and progesterone production as well, disruption ovulation.

Marijuana and the Endocannabinoid System (ECS)

The Endocannabinoid System (ECS) is responsible for regulating hormones and helps to keep the body in balance.

The endocannabinoid system is made up of three main parts:

  1. Cannabinoid receptors
  2. Endocannabinoids
  3. Metabolic enzymes

Cannabinoid Receptors

These receptors are found in cells throughout the body to receive cannabinoids to keep the body in a state of homeostasis. There are more cannabinoid receptors than any other type of receptor found in the brain.


Endocannabinoids are cannabinoids, much like those found in marijuana, which are produced by the human body to reduce and regulate inflammation (amongst other tasks).

Metabolic Enzymes

Metabolic enzymes are basically the go-between for cannabinoids and their receptors. They help eradicate the body of endocannabinoid waste after the compounds are no longer useful. This helps regulate the endocannabinoid system and keep it running smoothly.

So, when marijuana is ingested, the cannabinoids in the marijuana bind to the existing cannabinoid receptors in the body and can possibly upset this delicate balance.  The level of disruption depends on how much endocannabinoids are being produced naturally in the body, and how efficient your endocannabinoid system is.

The ECS is related to every other system in the body for balance, including how the reproduction system functions. The balance seems to be a little more precarious for women.  For an incredibly in-depth look at the endocannabinoid system and how it affects the female reproductive system – click here.

Marijuana Use During Pregnancy

Not surprisingly, there aren’t a lot of studies done on the effects of marijuana during pregnancy.   I’m sure you can appreciate the legal ramifications and lack of volunteers for such a study.

However, research has been done on how THC (the active ingredient in marijuana which gives you the “high” feeling) can affect pregnant women.  One important finding is that THC can cross the placenta barrier during pregnancy.

Exposure to THC during the developmental phase can cause issues such as:

  • Reduced growth

  • Premature labor

  • Lower birth weight

Impact of Cannabis Use on Male Fertility

The generally accepted view on marijuana and male fertility is that cannabis has a negative impact on sperm count and quality.

Many studies examining the impact of marijuana on fertility exist in rat models.   From these studies, it has been hypothesized that high concentrations of THC resides in the epididymis of these rats – an important structure necessary for sperm production.  Rats with higher levels of THC in their epididymal tissue reported significantly poorer sperm parameters. 

Marijuana use has also been said to decrease libido and increase impotence.

Is there evidence to support these claims?

Incidents of infertility have been trending up over the last few decades. More cases of couples struggling with infertility are being reported all the time.

Let’s take a closer look at some studies and recent trends to get a better idea of the big picture.

One study done in Europe on a sample of over 40,000 men yielded some interesting results.  Let’s take a closer look at what this study discovered.

General Trends in Sperm Count

This study involved taking sperm samples of these 40,000+ men over a 38-year period from 1973 – 2011.  Sperm Concentration and Total Sperm Count were used as measures to determine semen quality.

The results showed the following:

A 52.4% decrease in Sperm Concentration in the males tested over that time period.

A 59.4% decline in Total Sperm Count for the same males over the same time period.

We all expect sperm parameters to be affected by age a little but I think we can all agree that those results are a little shocking.

So, over the last few decades, male fertility seems to have been on the decline.   Moreover, some may say that marijuana use has been on the rise due to increased accessibility and more permissive attitudes towards the substance.

Could there be a correlation?

While increased cannabis use may have played some role in shrinking sperm counts, there are obviously many other factors contributing to this decline.

Other major factors known to impact sperm health include:

  • Poor diet
  • Lack of exercise
  • Unhealthy lifestyle choices (smoking and alcohol to name just two)

Danish Study on Semen Quality

A semen quality study was done in Denmark  between 2008 and 2012 on 1215 men between the ages of 18 and 28.

The study showed that regular cannabis use (more than once a week), was associated with a 28% decrease in sperm concentration, and a 29% decline in total sperm count.   Some sobering numbers to say the least.

Effects of Marijuana on Sperm Motility

Sperm motility refers to the ability of the sperm to move about effectively. Progressive sperm motility involves sperm swimming in a straight line, in a forward direction.

This 2006 study in the Journal of Fertility and Sterility was done on 78 males to test the effects of THC (the active ingredient in marijuana) on sperm function and quality.

The results of this study showed a decrease of anywhere from 2-28% in progressive sperm motility after exposure to THC.  Another reason for men to be careful with their cannabis use.

Effects of Marijuana on Time to Pregnancy for Both Women and Men

Time to pregnancy refers to how long it takes to get pregnant for a couple trying to conceive.

The question here is to determine if using cannabis can affect time to pregnancy.

A 2018 study, also in the Journal of Fertility and Sterility, was done to gain more insight into this question. A sample of 1,076 women and 758 men currently trying to conceive were analyzed.

The results surprisingly showed that marijuana use did not seem to impact the amount of time it took to become pregnant. 

Another study on the effects of cannabis on time to pregnancy was carried out at the Boston University, with similar results.

But, this raises a number of other questions like:

  • How often was marijuana being used?
  • How much marijuana was being consumed per session?
  • What was the method of consumption?
  • What was the THC level and was it consistent for all users?
  • Does the chance of infertility increase if both partners are chronic users?

And perhaps more importantly…

  • Did the couples who became pregnant make it to term?
  • Did they have any complications during the pregnancy or labour?

Perhaps they could look at these couples retrospectively and find these answers out.

The Final Say on Marijuana & Fertility

One might say there are problems with some of the studies on the effects of marijuana use on fertility.  The lack of detail about amount, frequency, and THC levels of the cannabis being used being one of them.

Nevertheless, it is safe to say that if you are struggling with infertility, refraining from marijuana use will very likely improve your situation.  

Numerous studies indicate that marijuana use can negatively impact fertility for both men and women so it is best to abstain.

Thankfully, a lot of the research indicates that cannabis-related issues with infertility are not permanent.  Just because you may have indulged in frequent marijuana use when you were younger, doesn’t mean it will have lingering effects when you finally decide to start trying to have a baby.

For an extremely in-depth look at cannabinoids and fertility – check out this 2010 article in Pharmaceuticals