Does THC Affect Fertility?

With the growing popularity of cannabis, many people are asking: does THC affect fertility? Whether you're planning to conceive or just thinking ahead, it's a valid concern. THC (tetrahydrocannabinol), the psychoactive compound in cannabis, interacts with several systems in the body—including those involved in reproduction.

Although research is ongoing, current studies suggest that regular cannabis use may affect both male and female fertility, particularly when used frequently or over a long period. Here's what we know so far.

How THC Affects the Male Reproductive System

In men, fertility is largely influenced by sperm count, motility (movement), shape, and hormonal balance. THC may interfere with several of these.

Sperm Quality

Studies have shown that regular cannabis use can lead to lower sperm count and reduced motility. In some cases, sperm produced by cannabis users may also show abnormal shapes, which can affect the ability to fertilise an egg.

Hormone Disruption

THC may affect levels of testosterone and luteinising hormone (LH), both of which are important for sperm production. Lower testosterone can also impact libido and sexual performance.

Endocannabinoid System

The body’s endocannabinoid system helps regulate various functions, including reproduction. THC, which mimics natural endocannabinoids, may disrupt this system, potentially affecting sperm production and hormonal signalling in the testes.

How THC Affects the Female Reproductive System

In women, fertility depends on ovulation, hormone cycles, and the health of the uterus and fallopian tubes. THC may interfere with several of these mechanisms.

Ovulation and Hormone Balance

Some research suggests that cannabis use can disrupt the menstrual cycle, delaying or suppressing ovulation. This could make it more difficult to conceive. THC may also interfere with the release of key reproductive hormones, such as oestrogen, progesterone, and LH.

Implantation and Early Pregnancy

Animal studies indicate that THC might impact the ability of a fertilised egg to implant in the uterus. In humans, cannabis use in early pregnancy has been associated with increased risk of miscarriage, though data is still limited.

Endometrial Receptivity

Some studies suggest THC could affect the uterine lining, making it less receptive to embryo implantation, although more research is needed in humans.

What About Occasional Use?

Most of the research linking cannabis to fertility issues focuses on chronic or heavy use. Occasional or infrequent use is less likely to have a measurable effect on fertility, but this doesn’t mean it’s risk-free—especially if use occurs during key stages of the menstrual cycle or just before conception.

If you're actively trying to conceive, healthcare professionals usually recommend avoiding all cannabis use to reduce the risk of complications.

Can THC Affect IVF or Assisted Fertility Treatments?

Yes. Some fertility clinics advise both partners to avoid cannabis for at least three months before IVF or other treatments. In men, this time frame allows for a full cycle of sperm regeneration. In women, it ensures hormonal balance and proper ovulatory function.

THC may also reduce the success rate of in vitro fertilisation, though more studies are needed to confirm the extent.

Is the Impact Reversible?

In many cases, yes. Research suggests that sperm quality and hormone levels can recover within a few months of stopping cannabis use, especially in younger men. In women, menstrual cycles often return to normal within one to two cycles after quitting.

However, long-term or heavy use may take longer to reverse. It’s important to speak to a GP or fertility specialist if you have concerns about delayed conception or irregular cycles.

What If You’re Already Pregnant?

Cannabis use during pregnancy is not recommended. THC can cross the placenta and affect the developing brain of the foetus. Some studies suggest increased risks of:

• Low birth weight

• Preterm birth

• Developmental delays

• Behavioural or cognitive problems in early childhood

Even if cannabis helps with nausea or anxiety, it’s best to seek medical alternatives during pregnancy and discuss options with your midwife or GP.

UK Legal Context

In the UK, THC is a Class B drug, and recreational use is illegal. Medical cannabis is legal only in limited, specialist-approved cases. Unregulated cannabis may be stronger than expected and can contain unknown additives, making its effects on fertility even harder to predict.

Final Word

THC can affect fertility in both men and women—particularly when used heavily or frequently. From reduced sperm quality to disrupted ovulation, cannabis can interfere with the body's natural reproductive rhythms. If you're planning to start a family, cutting back or quitting is a wise choice.

While occasional use might not have a major impact for everyone, fertility is sensitive to even small hormonal shifts, and cannabis isn’t risk-free. If you’re struggling to conceive, speak to a healthcare provider about your options and how lifestyle changes—like stopping cannabis—could help improve your chances.