Delta-9 THC can be detected and quantified in the semen of men who are chronic users of inhaled cannabis

Abstract

Purpose

The purpose of this proof-of-concept study was to determine whether delta-9-tetrahydrocannabinol (THC) and THC metabolites (11-OH THC and THC-COOH) can be detected in semen.

Methods

Twelve healthy men aged 18–45 years who identified as chronic and heavy users of inhaled cannabis were recruited. THC and THC metabolite levels were measured in serum, urine, and semen of the participants. Semen analyses were performed. Serum reproductive hormones were measured.

Results

The median age and BMI of participants were 27.0 years and 24.7 kg/m², respectively. Over half the participants were daily users of cannabis for over 5 years. Serum reproductive hormones were generally within normal ranges, except prolactin, which was elevated in 6 of 12 participants (mean 13.9 ng/mL). The median sperm concentration, motility, and morphology were 75.5 million/mL, 69.5%, and 5.5%, respectively. Urinary THC-COOH was detected in all 12 participants, and at least one serum THC metabolite was present in 10 of 12 participants. Two semen samples had insufficient volume to be analyzed. THC was above the reporting level of 0.50 ng/mL in the semen of two of the remaining participants. Seminal THC was moderately correlated with serum levels of THC (r = 0.66), serum 11-OH THC (r = 0.57), and serum THC-COOH (r = 0.67). Seminal delta-9 THC was not correlated with urinary cannabinoid levels or semen analysis parameters.

Conclusion

This is the first study to identify and quantify THC in human semen, demonstrating that THC can cross the blood-testis barrier in certain individuals. Seminal THC was found to be moderately correlated with serum THC and THC metabolites.

Introduction

Marijuana (Cannabis sativa) remains the most commonly used drug in the world, with 192 million people reporting its use in 2016 [1]. Men of reproductive age are the most prevalent consumers of marijuana [2], with 19.4% of adult men in the USA reporting use [1]. In accordance with the perception that marijuana poses few health risks, marijuana use has increased over the past decade: the number of Americans reporting use within the past month increased from 14.5 million to 19.8 million between 2007 and 2013, and the number reporting heavy use (over 20 days in the past month) increased from 5.1 to 8.1 million people [3]. This has been in part driven by the rapidly increasing public support for legal recreational use of marijuana, and the corresponding legalization reforms that have expanded access to recreational marijuana in now ten state-level jurisdictions [4].

The prevalence of marijuana use in reproductive-aged people underscores the importance of understanding its effect on human reproduction. In one study, 16.5% of men and 11.5% of women reported using marijuana while attempting to conceive [5]. Furthermore, emerging animal data have suggested that even brief paternal exposure to THC may cause long-lasting neurobehavioral effects in offspring, suggestive of intergenerational epigenetic changes that may be mediated by marijuana use [6]. While some human studies have suggested a deleterious effect of marijuana use on fertility or testicular function, evidence linking marijuana to reproductive outcomes is scarce and to date, often conflicting. A study of over 1200 healthy young Danish men found that those who smoked marijuana regularly had lower sperm concentrations and total sperm counts [7]. Meanwhile, another recent study evaluating 662 subfertile men in Massachusetts (with older average age than the prior study) found that men who had ever smoked marijuana had significantly higher sperm concentrations and total sperm counts than men who had never smoked marijuana [8]. Another contemporary national survey found no association between marijuana use while trying to conceive and overall fecundity [5]. A study of female patients undergoing in vitro fertilization found that current marijuana users had more than double the adjusted probability of pregnancy loss (54% versus 26%) when compared with those who were past marijuana users or had never smoked marijuana, but only nine women were included in the current users’ group [9].

The mechanism by which marijuana may disrupt reproduction is not entirely clear but is purported to be through its disturbance of the endocannabinoid system (ECS). The psychoactive component of marijuana is delta-9-tetrahydrocannabinol (THC or delta-9 THC), an exogenous cannabinoid which competes with endogenous endocannabinoids to bind to the CB1 and CB2 G protein-coupled cannabinoid receptors [10, 11]. These receptors are located throughout the body, including in the nervous system and reproductive tract, and the signaling system is likely involved with a broad array of functions [12, 13]. Endocannabinoids themselves have been detected throughout the human reproductive tracts in matrices such as follicular fluid [14, 15] and seminal fluid [16], highlighting their importance. Disturbances of the naturally occurring ECS can be linked to pregnancy loss, ectopic pregnancy, and other markers of reduced fertility [17–19]. Furthermore, animal models have suggested that the ECS plays a critical role in spermatogenesis and the fertilization process [20–22].

The role of endocannabinoids in the regulation and maintenance of fertility and early pregnancy has been fairly well studied, but data on the effects of exogenous cannabinoids such as THC are still limited mostly to in vitro and animal studies. As a critical first step toward better understanding the downstream consequences of marijuana on male fertility, spermatogenesis, and fertilization capacity, we sought to determine whether THC could be detected in human seminal fluid. The aim of this pilot, proof-of-concept study was to determine whether THC can cross the blood-testis barrier, and if THC and its metabolites can be identified and quantified in the seminal fluid of heavy marijuana users, whether levels are correlated with urine or serum concentrations.

Methods

Study participants

Healthy men aged 18–45 with a history of chronic and heavy inhaled cannabis use (at least 4 times per week for the past year at a minimum) were eligible to participate. Men with a history of infertility, testicular surgery or trauma, class III obesity (body mass index greater than 40.0 kg/m²), liver, or renal disease were excluded. Those with any recreational drug use aside from marijuana, as well as those with current heavy alcohol use (exceeding 14 drinks per week) or recent tobacco cigarette use (within 1 year), were excluded. Study participants were recruited using the Partners Healthcare Rally for Research online platform. Recruitment occurred between December 2018 and January 2019. The sample size was determined based on the cost of enrolling subjects, analysis, and the funding that was received and set at twelve participants. The study was approved by the Partners Healthcare Institutional Review Board.

Study design and procedures

This was a pilot, proof-of-concept study in which eligible participants presented to Brigham and Women’s Hospital (BWH) for a single study visit. Prior to this visit, initial eligibility screening occurred through structured telephone interviews. Participants were asked to plan for a period of between 48 and 72 h of abstinence from their last ejaculation before their scheduled study visit and to use cannabis within 24 h of their study visit. Written informed consent was obtained from all individual participants included in the study. The study was conducted in the BWH Reproductive Endocrinology Laboratory and the BWH Center for Clinical Investigation Clinical Trials Hub.

At presentation, participants were asked to fill out a written survey detailing their marijuana use. This form was an abbreviated version of the Daily Sessions, Frequency, Age of Onset, and Quantity of Cannabis Use Inventory (DFAQ-CU), a validated inventory in measuring quantity and frequency of cannabis use [23]. Participants were asked to provide a urine sample followed by a semen sample by way of masturbation into a collection container. After a successful collection of urine and semen samples, participants provided a serum sample. Venipuncture occurred within 20 min of providing the semen sample and was done between 7:30 and 10:00 in the morning for all participants.

Sample analysis

Semen analysis was performed in the usual fashion per the Brigham and Women’s Hospital Reproductive Endocrinology Laboratory Standard Operating Protocol. Semen specimens were evaluated visually and allowed to liquefy at room temperature for up to 60 min. The volume and viscosity of ejaculate were measured using a graduated sterile pipette. Six to seven microliters of the well-mixed specimen were deposited onto a standard count slide and loaded into the counting chamber of a Hamilton-Thorn IVOS Semen Analyzer. The sperm concentration measurement was performed in duplicate. Per protocol, if the sperm concentration was < 20 million/mL, the sperm concentration, motility, and forward progression assessments were performed manually. Sperm morphometry was performed on slides fixed with 5 μL of well-mixed semen smeared across the slide. The strict morphology of sperm morphology (Kruger’s criteria) was used [24, 25]. Semen parameters were quantified in nine categories: semen volume, semen pH, semen round cells, leukocytospermia, sperm concentration, sperm motility, sperm velocity, sperm linearity, and sperm morphology. The total motile sperm count (TMSC) was calculated. Furthermore, semen viscosity and agglutination were evaluated.

The remainder of ejaculate not used for analysis, as well as urine and serum samples, was frozen and stored at − 80 °C. All samples were batched together for the THC and THC metabolite assays. While there are over 100 metabolites of THC, the dominant metabolites in serum are 11-hydroxy delta-9 THC (11-OH THC) and delta-9 carboxy THC (THC-COOH). The main metabolite of THC in urine is THC-COOH. Cannabinoid assay testing was performed with high-performance liquid chromatography/tandem mass spectrometry (LC-MS/MS) by NMS Labs (Willow Grove, PA). Analytes were measured by a Sciex 4500 Mass Spectrometer with a Shimadzu Prominence Ultra-Fast Liquid Chromatography System and equipped with Electrospray Ionization ion source. The quantification range was 0.50–50 ng/mL for serum/semen delta-9 THC, 5.0–500 ng/mL for serum/semen THC-COOH, 1.0–100 ng/mL for serum/semen 11-OH THC, and 5.0–500 ng/mL for urinary THC-COOH. Urine creatinine was also analyzed via colorimetry by NMS Labs to calculate a corrected ratio to account for the variable dilution of urine.

Serum samples were evaluated for steroid hormones through the Brigham Research Assay Core (BRAC) laboratory (Boston, Massachusetts). Serum estradiol (E2), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, and sex hormone-binding globulin (SHBG) were measured for each study participant using electrochemiluminescence immunoassay (ECLIA) (assays manufactured by Beckman Coulter, Fullerton, CA). Serum total testosterone was measured for each participant using liquid chromatography-tandem mass spectrometry. The freezing of serum samples at − 80C until the time of assay does not impact the ECLIA or LC-MS results. The intra-assay and inter-assay variations of these samples were less than 8.0% for all batches in all assays run.

Results

Twenty-three men underwent phone screening after responding to initial recruitment efforts and eight were disqualified based on the phone screen. Of the remaining fifteen, twelve were enrolled and completed the study. The remaining three participants were not enrolled because goal participation had been reached, as determined by the cost of enrolling subjects, performing the analyses, and the funding that was received.

The demographics of the study population are shown in Table 1. The median age of participants was 27.0 years and the median body mass index (BMI) was 24.7 kg/m². Most participants were White. On average, participants used marijuana 10 h prior to their study visit and abstained for a period of 53 h from ejaculation. Most participants identified themselves as regular consumers of marijuana for at least 5 years with at least 2000 lifetime episodes of marijuana use. Ten of twelve used marijuana at least five times in the week prior to their study visit, and all had used between 25 and 30 days of the last month.

Table 1.

Characteristics of study participants (N = 12)

Characteristic	Median, mean, SD (range)
Age (years)	27.0, 28.7, 5.4 (22.8–37.1)
BMI (kg/m2)	24.7, 25.4, 4.4 (19.0–37.0)
Ethnicity, n (%)
White	8 (66.7)
Asian	2 (16.7)
Mixed ethnicity	2 (16.7)
Time since marijuana use (hours)	10.0, 9.8, 2.8 (2–12)
Time since prior ejaculation (hours)	53.0, 58.3, 20.9 (24–96)
Marijuana usage pattern	n (%)
Years of marijuana use
1 year	1 (8.3)
1–2 years	2 (16.7)
2–5 years	2 (16.7)
5–10 years	6 (50.0)
More than 10 years	1 (8.3)
Days of marijuana usage in the past week
<5	2 (16.7)
5–6	2 (16.7)
7	8 (66.7)
Lifetime number of marijuana uses
< 1000	2 (16.7)
1000–2000	2 (16.7)
2000–5000	3 (25.0)
5000–10,000	5 (41.7)

Semen analysis parameters are shown in Table 2. All participants had a normal sperm concentration (over 15 million/mL), and one of twelve had asthenozoospermia (motility of 22%) with a resulting total motile sperm count (TMSC) of six million. Two participants were noted to have slightly viscous semen, and none had agglutination. A range of morphology was seen, from 1 to 10%, with seven of twelve having more than 4% normal forms.

Table 2.

Semen analysis parameters of study participants

Semen analysis parameter	Median, mean, SD (range)	Reference range
Semen volume (mL)	2.0, 2.3, 1.4 (0.5–6.0)	2.0–5.0
Semen pH	8.0, 8.2, 0.3 (8.0–8.5)	7.2–8.0
Sperm concentration (million/mL)	75.5, 76.8, 44.8 (20.0–132.0)	20–500
Sperm motility (%)	69.5, 66.5, 19.1 (22.0–93.0)	50–100
Sperm morphology (% normal)	5.5, 5.2, 2.4 (1–10)	5–100
Total motile sperm count (million)	113.5, 116.3, 84.5 (6.0–240.6)

The serum and urine concentrations of THC and THC metabolites are shown in Table 3. Urine THC-COOH was present in all twelve participants and demonstrated a wide range. This was true even when corrected for urine creatinine. Serum THC was detected in nine participants, serum THC-COOH as detected in nine participants, and serum 11-OH THC was detected in five of twelve participants. Serum THC was strongly correlated with serum 11-OH THC (r = 0.98) and serum THC-COOH (r = 0.95); serum 11-OH THC was strongly correlated with serum THC-COOH as well (r = 0.91); and urine THC-COOH was moderately correlated with serum THC-COOH and serum THC (r = 0.66, r = 0.52, respectively) and strongly correlated with serum 11-OH THC (r = 0.91).

Table 3.

Serum, urine, and semen concentrations of THC and THC metabolites in study participants

THC metabolite	Median, mean, SD (range)	Units	Reporting limit
Serum, delta-9 THC	1.6, 2.9, 5.3 (0–19.0)	ng/mL	0.50
Serum, delta-9 carboxy THC	20.5, 29.8, 38.6 (0–140.0)	ng/mL	5.0
Serum, 11-hydroxy delta-9 THC	0.0, 1.5, 3.1 (0–11.0)	ng/mL	1.0
Urine, delta-9 carboxy THC*	155.0, 252.8, 221.7 (11–> 500)	ng/mL	10
Urine, 11-hydroxy delta-9 THC corrected by urine creatinine*	104.3, 108.4, 84.3 (6.7–250.3)	ng/mg of creatinine	----
Semen, delta-9 THC**	0.87–0.97	ng/mL	0.50

*Urine delta-9 carboxy THC had an upper limit of detection of 500 ng/mL. For any results reported as > 500 ng/mL, they were treated as = 500 ng/mL

**Reported as range only as there were only 2 patients with detectable delta-9 THC

Semen could not be assayed for cannabinoids in two of twelve participants due to an inadequate sample volume (NMS Labs required a minimum of 500 μL of semen to adequately process the samples; two participants had hypospermia and pre-analysis ejaculatory volumes of 500 μL and 600 μL and did not meet this minimum requirement after initial processing). Of the remaining ten, semen THC was detected in two samples at concentrations of 0.87 and 0.97 ng/mL. The baseline characteristics of these two subjects with detectable semen THC are demonstrated in Table 4. Semen THC was moderately positively correlated with serum THC (r = 0.66), serum THC-COOH (r = 0.67), and serum 11-OH THC (r = 0.57). There was a weaker association between semen THC and corrected urine THC-COOH to creatinine ratio (r = 0.35) and time since prior ejaculation (r = 0.46). There was no correlation between semen THC and uncorrected urine THC-COOH, time since last marijuana exposure, participant age, or participant BMI.

Table 4.

Baseline characteristics of study subjects with detectable semen THC

Characteristic	Subject 1	Subject 2
Semen THC (ng/mL)	0.97	0.87
Age (years)	25.6	37.1
BMI (kg/m2)	23.0	25.6
Time since marijuana use (hours)	12	10
Time since prior ejaculation (hours)	50	96
Years of marijuana use	5–10 years	5–10 years
Days of marijuana usage in the past week	7	7
Lifetime number of marijuana uses	5000–10,000	5000–10,000

Serum reproductive hormone profiles are shown in Table 5. All participants had FSH, estradiol, total testosterone, and SHBG values that were within the normal reference range. One of twelve’s LH was slightly below the reference range. Six of 12 participants had elevated prolactin levels beyond the reference range, and the mean prolactin of the whole cohort was slightly elevated beyond the upper range of normal.

Table 5.

Serum reproductive hormones in study participants

Hormone	Median, mean, SD (range)	Units	Normal reference range
Estradiol	31.31, 30.59, 7.83 (20.06–42.00)	pg/mL	20–47 pg/mL
FSH	2.81, 2.86, 1.05 (1.44–5.19)	mIU/mL	1.27–19.26 mIU/mL
LH	3.81, 3.69, 1.32 (1.17–6.33)	mIU/mL	1.24–8.62 mIU/mL
Total testosterone	578.50, 581.08, 155.94 (317–884)	ng/dL	270–1070 ng/dL
Free testosterone (calculated)	13.02, 13.00, 3.08 (9.11–18.98)	ng/dL	----
SHBG	26.24, 31.32, 14.19 (13.75–66.12)	nmol/L	13.3–89.5 nmol/L
Prolactin	12.37, 13.89, 9.22 (5.88–41.05)	ng/mL	2.64–13.13 ng/mL

Free testosterone was moderately negatively correlated with TMSC (r = − 0.41) but was not correlated with sperm concentration or motility. There was no correlation between LH, FSH, or prolactin and semen parameters. Free testosterone was weakly negatively correlated with urine THC-COOH (r = − 0.31) and not correlated with serum or semen THC or THC metabolites.

Discussion

In this proof-of-concept pilot study, we found that THC can cross the blood-testis barrier in certain individuals and can be detected and quantified in the seminal fluid of some, but not all, heavy users of inhaled marijuana. In the setting of a growing repository of data surrounding the effects of the endocannabinoid system in the regulation and maintenance of fertility and early pregnancy, ours is the first report that the exogenous cannabinoid THC can be detected in any human reproductive matrix.

Our study found that in the two participants whose semen samples contained measurable THC, there were no reliable demographic characteristics, semen, or hormonal parameters that might predict the presence of THC in seminal fluid. Semen THC was only moderately correlated with serum THC and THC metabolite levels and not correlated with urinary THC-COOH. Our study consisted of only heavy users; thus, we could not deduce a pattern linking frequency or dosage of use with the presence of THC in seminal fluid since all participants used marijuana at least four times a week. Both participants with measurable semen THC had been using marijuana at that frequency for at least 5 to 10 years. However, there were five additional participants whose semen did not test positive for THC who had chronically used marijuana for at least the same duration. Within our study, most participants had used marijuana at least 8 h prior to producing their ejaculated sample (only one participant used marijuana 2 h prior), and all participants abstained from ejaculation for 48 h prior to their study visit. Our study is unable to assess whether a shorter duration between usage and ejaculation might significantly affect the detection or the absolute levels of THC in semen.

We found a wide variation in serum and urinary levels of THC and THC metabolites. Large variations in serum and urine levels are to be expected from what is known about the complex pharmacokinetics and pharmacodynamics of THC [26]. This is due to a variety of factors affecting absorption, including significant variations in the efficiency of smoking techniques [27, 28], different strains, potency, and concentrations of cannabis product. Even in controlled experiments with standardized cannabis cigarettes, there is considerable variation in absorption among individuals and a poor relationship between THC dosage and peak plasma THC levels [29]. Prior pharmacokinetic studies have demonstrated that THC and THC-OH are excreted in the urine for up to 24 days in chronic, heavy cannabis users [30]; THC-COOH is detectable in urine for up to 3 days (after single consumption) and up to 30 days (after frequent, daily consumption) [31–33]. Plasma levels are more reliable than urine, but the T_max is much shorter, reported as short as 5 min in some studies [34]. Thus, the wide variation of serum and urinary levels that were seen in our study population, as well as the weak correlation between serum and urine levels, is to be expected.

No other studies have measured THC directly in semen, although endocannabinoid receptors have been identified in human testes and on sperm [11, 35]. THC has been implicated in lowering sperm counts and concentrations [36, 37], affecting sperm morphology [38], reducing motility [39], and decreasing sperm fertilizing capacity [35, 40, 41]. However, studies examining the direct effect of THC on human sperm are limited. In one prior study, the addition of THC to washed semen samples inhibited sperm mitochondrial oxygen consumption [42]. Another study found that after incubating sperm in vitro with THC directly at three different concentrations (two to mimic plasma levels after recreational use and one to mimic levels after therapeutic use), percentage progressive motility and spontaneous acrosome reactions were decreased in a dose-dependent manner [39]. Our study lends credence to the studies preceding it, as it demonstrates that THC can be detected in the seminal fluid itself in certain individuals. However, it should be noted that even the lowest concentration of THC with which former studies incubated sperm was over tenfold higher than the concentration of THC detected in the semen of our study subjects.

The effect of marijuana on human gametes and fertilization is relatively unknown. One prospective study of 221 patients undergoing assisted reproductive technology found that users of marijuana experienced a 28% lower fertilization rate [43]. However, the exact mechanisms accounting for poorer fertilization could not be elucidated. Our findings, that THC can be directly quantified in human seminal fluid, lay the groundwork to allow for future studies. Since THC can be detected in the seminal fluid of some individuals, this might provide a direct method of measurement (rather than relying on self-reporting marijuana use, which is subjective and potentially unreliable, or serum levels which only reflect recent exposure) to bridge real-world clinical studies with the prior staged studies in which THC was directly incubated with washed sperm.

It is puzzling that some, but not all, semen samples tested positive for THC. There were no obvious factors that were strongly associated with detectable semen THC; thus, we can propose few predictors of the presence of THC in human semen. Future directions include identifying characteristics that may affect semen detectable THC levels. Further pharmacokinetic and pharmacodynamic studies are also possible, now that we have taken the first step to prove that THC can be detectable in human reproductive matrices in some cases.

While our proof-of-concept study did investigate the potential for disturbances in the serum reproductive hormone profiles of chronic, heavy marijuana users, our study was limited by the lack of a matched control group of never or occasional users. In our cohort, all twelve participants had normal range FSH and estradiol values. Prior studies have suggested that cannabis has no effect on plasma FSH levels but does reduce plasma LH levels [44]. Indeed, we did have one participant with a low plasma LH level, though this could also be due to chance given our small cohort size. Notably, the CB1 receptor has been located in the LH-secreting gonadotrophic cells in the anterior pituitary [45], and further studies examining the effect of chronic marijuana use on gonadotropins may be of interest.

Several early studies suggested that marijuana use led to a dose-dependent reduction in plasma testosterone levels, but more recent studies have shown either no difference or a rise in testosterone levels [7, 36, 46–48]. In our study, all participants had normal total testosterone and SHBG, although our cohort might have been too small to detect a subtle effect. We did find that six of twelve participants had prolactin levels beyond the reference range, and the mean prolactin for the cohort was elevated. Preceding studies have been mixed in demonstrating the effect of chronic marijuana use on serum prolactin levels, with some showing higher, others lower, and still others with no change in prolactin levels [49–51]. While the mechanism through which chronic marijuana use may affect prolactin is poorly understood, one hypothesis is that THC may initially activate, and then, with chronic exposure, eventually blunt the dopaminergic system, thus affecting downstream regulation of prolactin [52]. Further studies are indicated to better understand the effect of THC on neuroendocrine control of the reproductive axis in both men and women.

There are important limitations to our study to note. This was designed and executed as a proof-of-concept study to assess whether THC could be detected in semen. By design, our study enrolled only chronic and heavy users of marijuana—those subjects we felt would provide the highest chance of detecting THC in bodily fluids. Consequently, our study findings cannot be generalized to include ever users, light, or moderate users of marijuana. We also did not design this study to compare types of cannabis use—all our participants most regularly used inhaled cannabis, and future studies might examine the effect of edibles or concentrates on the identification of THC in tissues. Furthermore, our study numbers are very small; this was due to this being a pilot study with the intention to expand upon our findings with a larger cohort if THC were detectable in semen. Thus, our conclusions are limited by the size of this proof-of-concept study. There was a lack of racial diversity, further limiting our conclusions. We did not have a control group; thus, our findings about serum reproductive hormones and semen analysis results are observational. Our questionnaire did not assess for the cannabis strains utilized nor did our study control for potency. A controlled situation would be to utilize a dose and strain-controlled cannabis cigarette. Lastly, we tested seminal fluid for cannabinoids without washing or processing the semen sample, as is typically done in preparation for intrauterine insemination or in vitro fertilization.

A strength of this proof-of-concept study was that we obtained multiple body fluid samples at the same time point, which allowed us to compare contemporaneous serum, urine, and semen cannabinoid levels and the associated serum reproductive hormones. Another strength was that the study questionnaire assessing marijuana use was based on quantifiable methods that have been validated in prior studies [23]. Furthermore, the testing of serum and urinary THC and THC metabolites levels confirmed that all our participants were users of marijuana (rather than relying on self-reported use). Finally, our cannabinoid testing was done by an outside laboratory (NMS Labs) with assays that are commercially available, thereby allowing generalizability and future studies that could be performed by others.

Research on the effects of cannabis use on human reproduction is still in its infancy but will become increasingly important as the legalization of recreational marijuana expands access. Prior studies have either focused on animal studies or direct incubation of sperm with THC at levels that may not reflect actual in vivo THC levels in users. Large cohort studies are apt to study trends among populations but are dependent on personal reporting of marijuana use, which is subject to honest disclosure and recalls bias. Further efforts are needed to understand whether THC can also be directly quantified in other reproductive tissues and fluids, and if so, the IVF embryology lab may provide the ideal opportunity to assess the effects of THC on egg maturity, quality, fertilization, embryo development, and implantation potential. The ability to quantify cannabinoids in human reproductive tissues and fluids gives us the capability to directly study the effects of cannabis on early human reproduction.

Funding information

This study was funded by the Expanding the Boundaries Grant Phase XXVIII from the Brigham and Women’s Hospital, Department of Obstetrics and Gynecology, and with special thanks to Debbie and Keith Gelb for their generous financial support.

Compliance with ethical standards

Human and animal rights and informed consent statement

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee (Partners Healthcare Institutional Review Board) and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.