In women of reproductive age, cannabis is the most commonly used recreational drug, and there the use of cannabis during pregnancy is on the rise.    While recent studies have suggested that cannabis use during pregnancy may pose risks to the developing fetus, less is known about the impact of cannabis on fertility.

Up until very recently, only three studies (Klonoff-Cohen et al 2006; Kasman et al 2018; Wise et al 2018) have examined the impact of marijuana use on fertility. Two of the studies found no evidence that either partner’s marijuana use affected the time to achieve pregnancy (Kasman et al 2018; Wise et al 2018). While these studies assessed couples attempting to conceive naturally, the third study (Klonoff-Cohen et al 2006) looked at couples undergoing ART, reporting that marijuana smoking was related to lower oocyte yield and lower fertilization rate but did not ultimately impact pregnancy or live birth rates.  While this last study raises concerns, it was conducted in 2006 when approximately half of the couples underwent gamete or zygote intrafallopian transfer (GIFT/ZIFT) cycles, which now represents <1% of assisted reproductive technology (ART) cases.

A recent study has looked at the impact of smoking marijuana in a group of infertile couples undergoing ART.  This study included 421 women with a total of 730 ART cycles who were participants in a prospective cohort (the Environment and Reproductive Health Study) at a fertility center in Boston (2004-2017).  Participants, including the partners of 200 women, self-reported marijuana smoking at baseline. 

In this cohort, 44% of the women and 61% of the men had smoked marijuana at some point in their lifetime; 3% of the women and 12% of the men were marijuana smokers at the time of enrollment.  Among the 317 women (395 cycles) with a positive pregnancy test (positive B-hCG levels), the women who were marijuana smokers at baseline (N?=?9, cycles?=?16) had more than double the adjusted probability of pregnancy loss than those who were past marijuana smokers or had never smoked marijuana (N?=?308, 379 cycles) (54% vs 26%; P?=?0.0003). 

Interestingly, in couples in which the male partner was a marijuana smoker at enrollment (N?=?23, 41 cycles) had a significantly higher adjusted probability of live birth than couples in which the male partner was a past marijuana smoker or had never smoked marijuana (N=?177, 327 cycles) (48% vs 29%; P?=?0.04), independent of the women’s marijuana smoking status. 

Female Fertility

This study indicates that female marijuana users have about a twofold increase in risk of pregnancy loss.  This finding is consistent with studies carried out in the general population, demonstrating increased risks of miscarriage and stillbirth; however, the current study is very small, inclusing only 9 marijuana users.  

Male Fertility

Before jumping to conclusions and assuming that smoking marijuana might actually enhance fertility in men, there are some important things to consider.  First of all, this study was very small, including only 23 marijuana users. It would be important to see this finding replicated in larger populations. Furthermore, given that this study is based on self-reporting on marijuana use, we might not be seeing the full picture and might be underestimating the number of users.  (This study took place before recreational marijuana was legalized in Massachusetts.) In addition, only about half of the male partners provided information regarding cannabis use.  

While this study is consistent with previous studies and does not suggest that the use of marijuana by the male partner has a negative impact on achieving pregnancy and on rates of live birth, it is premature to conclude that marijuana use in the male partner is “safe” and does not negatively impact fertility.  

In fact, previous studies, looking specifically at male reproductive functioning have shown that use of cannabis, especially when chronic and/or heavy, may negatively impact male fertility across several domains.  Cannabis use has been associated with testicular atrophy, low libido, sexual dysfunction, and lower levels of various hormones required for reproduction, including testosterone. In addition, cannabis use has been associated with reductions in sperm count and concentration, abnormalities in sperm morphology, reductions in sperm motility and viability, and decreases in fertilizing capacity.

Bottom Line

We will continue to recommend that women (and their male partners) who are pregnant or attempting to conceive should not use cannabis.  

 

Ruta Nonacs, MD PhD

 

Kasman AM, Thoma ME, McLain AC, Eisenberg ML.  Association between use of marijuana and time to pregnancy in men and women: findings from the National Survey of Family Growth.  Fertil Steril. 2018 May;109(5):866-871. 

Klonoff-Cohen HS, Natarajan L, Chen RV.  A prospective study of the effects of female and male marijuana use on in vitro fertilization (IVF) and gamete intrafallopian transfer (GIFT) outcomes.  Am J Obstet Gynecol. 2006 Feb;194(2):369-76.

Nassan FL, Arvizu M, Mínguez-Alarcón L, Gaskins AJ, Williams PL, Petrozza JC, Hauser R, Chavarro JE; EARTH Study Team.  Marijuana smoking and outcomes of infertility treatment with assisted reproductive technologies.  Hum Reprod. 2019 Sep 29;34(9):1818-1829.

Payne KS, Mazur DJ, Hotaling JM, Pastuszak AW.Cannabis and Male Fertility: A Systematic Review.  J Urol. 2019 Mar 27:

Wise LA, Wesselink AK, Hatch EE, Rothman KJ, Mikkelsen EM, Sørensen HT, Mahalingaiah S.  Marijuana use and fecundability in a North American preconception cohort study.  J Epidemiol Community Health. 2018 Mar;72(3):208-215.