Marijuana may affect female fertility
Marijuana, also known as cannabis, is the most popular recreational drug worldwide after alcohol, caffeine and tobacco. But a new study published in the Journal of the Endocrine Society shows that marijuana may have a negative effect on fertility in females [1. Misner M, Favetta LA. MON-010 Effects of Delta-9-Tetrahydrocannabinol (THC) on Oocyte Competence and Early Embryonic Development. Journal of the Endocrine Society. 2020. 4(1)].
Why is this study significant?
The age of marijuana users
This is a particularly important area of research because marijuana is the most common recreational drug used by people who are in their prime reproductive years. Therefore if marijuana is proven to impair fertility, it could be responsible for a large proportion of unsuccessful attempts at conceiving.
The THC levels in marijuana
THC, or tetrahydrocannabinol, is the main psychoactive chemical in marijuana. This compound is responsible for the effects of marijuana in the human body, which include the feeling of euphoria and hallucinations, as well as its addictive properties.
Over recent years, the amounts of THC in marijuana has increased from around 2% THC content in the 1980s to around 20% THC content in the strains currently available. If THC damages fertility, these high THC levels would be particularly worrying.
What is the current advice on marijuana and fertility?
Generally the medical advice is to stop using marijuana if you are trying to conceive. The same advice applies if you are undergoing fertility treatments, as we do not yet fully understand how marijuana can affect the reproductive system.
However the research behind this advice is relatively weak. This is why we need more definite scientific data showing the effects of marijuana use on fertility.
What happened in the study?
This was an animal study
The scientists in this study analysed the effects of THC in an animal study. They used egg cells, or oocytes, from female cows.
The team treated these egg cells with different concentrations of THC. The levels of exposure to THC were the same as the blood plasma concentrations of THC after therapeutic and recreational doses of marijuana.
The egg cells were separated into five different groups:
The scientists measured a range of data
The team monitored the development of the egg cells in the different groups. In particular they analysed whether the egg cells were able to reach certain points in development within a specified time period.
The scientists also analysed the genes which were expressed by the egg cells. These genes are an important part of determining whether the cells can develop successfully.
What were the results of the study?
The development of the egg cells altered with THC
In the groups where egg cells were exposed to higher concentrations of THC, the scientists found that the development of the egg cells was negatively affected.
Fewer of these egg cells reached the expected development stages within the set time period, with many cells experiencing a delay in development.
Gene expression was affected by THC
The team focused on genes called connexins. In general, egg cells which are high in quality have a higher level of expression of connexins.
Overall the scientists found that exposure to THC led to a reduced expression of connexins, even if the THC exposure was low. The team also found that THC had a negative impact on 62 separate genes in the treatment groups.
What do the results mean?
The scientists found that exposure to THC slowed down the development of egg cells. It also reduced the expression of connexins in these cells.
This means that the quality of the egg cells is worse after exposure to THC. Egg cell quality is an important indicator of how likely it is that a pregnancy will be successful. In these cases, the embryos would be much less likely to develop successfully.
How important are these results?
This study was done on cows therefore the results are of limited use. We will only understand the full extent of the effects of THC when studies are carried out on human cells.
However this study is important as it analysed the effects of THC in detail on different aspects of fertility including egg development and genetic components. These aspects are relevant in human cells, and this study is an important first step into better understanding how THC can harm fertility.
When should I stop using marijuana?
The length of time that THC stays in the body can depend on a number of factors including:
The body metabolises THC in the liver with the help of enzymes. These enzymes break THC down into a number of different metabolites.
The half-life of a substance is the time it takes for the amount of substance to halve in the body. The half-life of the metabolites of THC can vary.
For infrequent users, the half-life of THC metabolites which are excreted in urine is 1.3 days. But the half-life can be longer for frequent users of marijuana, extending to as much as 10.3 days [2. Smith-Kielland A, Skuterud B, Mørland J. Urinary Excretion of 11-nor-9-carboxy-delta9-tetrahydrocannabinol and Cannabinoids in Frequent and Infrequent Drug Users. Journal of Analytical Toxicology. 1999. 23(5): 323-32].
This means that it can take the body weeks to fully clear THC metabolites from the cells. Scientists have detected metabolites in the urine for up to 30 days after using marijuana [3. Hadland SE, Levy S. Objective Testing- Urine And Other Drug Tests. Child and Adolescent Psychiatric Clinics of North America. 2017].
THC can linger in the body in other cells for an even longer amount of time. Like many drugs, it is harder to remove from human hair and it can be detected for as long as 90 days after marijuana use [4. Hadland SE, Levy S. Objective Testing- Urine And Other Drug Tests. Child and Adolescent Psychiatric Clinics of North America. 2017].
In most people, your body will remove THC from your bodily fluids in 30 days or less. This is the period of time when your reproductive cells will be most exposed to THC.
Therefore you should ideally stop taking marijuana for at least a month before you start trying to conceive. This is only a minimum guideline because the sooner you stop taking marijuana the better the chances are that your fertility will improve.
We do not know exactly how marijuana affects female fertility yet, but it is likely to be harmful. This study is a first step towards showing how marijuana may damage the quality of egg cells.
Therefore to maximise your chances of conceiving, you should stop taking marijuana as soon as possible. Alongside this, it would be a good idea to adopt a healthier lifestyle with a balanced diet and more exercise in order to increase your health and prepare your body for pregnancy.
Dr. Kooner is Deputy Director of The Advanced Fertility Center of Chicago and has been a Specialist in Fertility Treatment since 1999.
As well as the areas that the clinic specialises in general, he is particularly interested in managing oocyte donation, female same-sex couples, single women having sperm donation and those considering egg freezing.
Dr. Kooner regularly speaks at fertility meetings. He has published in national journals and constantly contributes to the fertility research and publications from Advanced Fertility Center of Chicago.