Marijuana use is increasing among women of reproductive age, yet its effects on fertility remain unclear. The primary psychoactive compound in cannabis, delta-9-tetrahydrocannabinol (THC), interacts with biological systems that govern the female reproductive cycle, creating a plausible mechanism for interference. This article focuses on how cannabis use may disrupt the biological processes required for conception. The evidence suggests that while the impact can be subtle, frequent or heavy use may introduce significant challenges for women attempting to become pregnant.
The Endocannabinoid System and Female Reproduction
The scientific basis for cannabis affecting fertility lies in the body’s natural signaling network known as the Endocannabinoid System (ECS). The ECS is a complex regulatory system composed of chemical messengers (endocannabinoids), enzymes, and cannabinoid receptors (CB1 and CB2). This system regulates fundamental reproductive processes, including the timing of the menstrual cycle, the development of ovarian follicles, and the preparation of the uterine lining for embryo implantation.
The receptors of the ECS, particularly CB1, are widely expressed across the female reproductive tract, including the ovaries, fallopian tubes, and uterus. THC acts as an external signal that mimics the body’s natural endocannabinoids, binding to and over-activating these receptors. This external interference disrupts the precisely timed levels of endocannabinoids required for successful reproduction. Cannabis use can throw the entire reproductive timeline off balance.
Impact on Hormones and Ovulation
The primary physiological disruption caused by cannabis use occurs within the hypothalamic-pituitary-gonadal (HPG) axis, which is the control center for female reproductive hormones. Acute exposure to THC has been shown to suppress or alter the pulsatile release of Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus. Since GnRH is the master signal, its suppression leads to a downstream reduction in the release of Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH) from the pituitary gland.
These hormonal shifts can have direct consequences for ovulation and the quality of the egg. Reduced FSH levels can impair the proper growth and maturation of the ovarian follicle, which houses the developing egg. A decrease in the pre-ovulatory LH surge, necessary to trigger the release of a mature egg, can result in anovulation, or the failure to release an egg entirely. Chronic exposure to cannabis has been associated with menstrual cycle irregularities and a prolonged follicular phase in some animal models, delaying conception.
THC exposure may also directly affect the quality of the oocyte (egg) itself. Studies have shown that THC metabolites can be detected in the follicular fluid, the liquid surrounding the egg in the ovary. Exposure to THC in this microenvironment has been linked to harmful cellular changes, including an increased rate of chromosome errors (aneuploidy) and spindle disruption in the egg. These defects can compromise the viability of a resulting embryo, even if fertilization occurs, potentially leading to a lower chance of a successful pregnancy.
Clinical Findings on Conception Success
Clinical research on cannabis use and female fertility is complex, often yielding conflicting results due to challenges like self-reporting and confounding factors such as concurrent tobacco consumption. Synthesizing the available human data reveals concerning trends, particularly with frequent use. Some large population-based studies have not found a clear association between general cannabis use and a prolonged time-to-pregnancy (TTP).
However, data suggests a different picture for women with more frequent use or those already facing fertility challenges. Heavy or daily cannabis use correlates with a longer TTP and reduced fecundability—the probability of achieving a pregnancy in one menstrual cycle—compared to non-users. For women undergoing assisted reproductive technology (ART), such as in vitro fertilization (IVF), cannabis use may be detrimental. Women who used cannabis prior to an IVF cycle were found to have a reduced number of eggs retrieved and a lower fertilization rate.
Guidance for Conception Planning
Given the biological mechanisms of disruption and the concerning clinical data, medical organizations recommend that women avoid cannabis use when attempting to conceive. The American College of Obstetricians and Gynecologists advises patients planning or trying to get pregnant to discontinue using cannabis products entirely. This recommendation applies to all forms of use, including smoking, vaping, and edibles, as THC can persist in the body’s fat stores for extended periods.
For women planning to undergo fertility treatments like IVF, abstinence is important during the preparation and stimulation phase. While THC clearance time is highly variable based on frequency of use and product potency, experts recommend stopping use at least one full menstrual cycle before an egg retrieval procedure. Eliminating cannabis exposure ensures the reproductive system has the best opportunity to function without external disruption to hormonal balance and oocyte maturation.