Does Weed Affect Female Fertility? What an NIH Study Found

Weed may make it harder for women to get pregnant: a National Institutes of Health study found that women who used cannabis had about 41% lower odds of conceiving in any given cycle than non-users. Researchers think THC may disrupt reproductive hormones and the uterine lining, though the number of users in the study was small. As more women turn to cannabis for pain, stress or just for fun, it's worth understanding how the plant might affect the ability to conceive.

Science is starting to shed light on how THC and other cannabis compounds interact with the female reproductive system, potentially altering menstrual cycles, ovulation and embryo implantation. Here's what the evidence actually says about smoking weed and female fertility, plus the possible risks and what to consider if you're trying to conceive.

Weed and female fertility: what do the studies say?

Using cannabis could make it harder for women to conceive, according to a study by researchers at the National Institutes of Health (NIH). The study, led by Sunni L. Mumford, PhD, of the Epidemiology Branch at the Eunice Kennedy Shriver National Institute of Child Health and Human Development, found that women who use cannabis have roughly 40% lower chances of conceiving per menstrual cycle than women who don't.

Published in the journal Human Reproduction, the study offers important findings on the link between cannabis and female fertility.

How the study worked

The study focused on women trying to conceive after one or two previous miscarriages. Unlike some other studies, it didn't look at whether the women's partners used cannabis. Participants were part of a larger trial that included more than 1,200 women aged 18 to 40 with a history of pregnancy loss.

The women were followed for up to six menstrual cycles while trying to get pregnant, and those who did were tracked through their entire pregnancy. At enrollment, they filled out a questionnaire about their cannabis use over the previous 12 months and gave urine samples at the start of the study and six months later, or at the time of a positive pregnancy test.

Does weed affect pregnancy? Key results

Of the 1,200 women studied, 62 (5%) tested positive in urine tests or reported using cannabis before conception. The results showed that cannabis users had 41% lower odds of conceiving per cycle compared with non-users.

On top of that, only 42% of cannabis users got pregnant during the study, versus 66% of non-users.

That said, there was no significant difference in miscarriage rates between users and non-users who did conceive. There were, however, notable hormonal differences: cannabis users had higher levels of luteinizing hormone (LH) and a higher ratio of LH to follicle-stimulating hormone (FSH), which may have affected their chances of conceiving.

So does weed lower fertility?

The study's authors note that cannabis use may alter reproductive hormones and the lining of the uterus (the endometrium), which could lower the odds of an embryo implanting. Animal studies have shown cannabis can affect the endometrium, reducing the chances of establishing a pregnancy.

Takeaways: weed and female fertility

The authors recommend that women trying to conceive be cautious about using cannabis until more definitive evidence is available.

While the results suggest a negative link between cannabis use and female fertility, the authors warn they should be read with caution because of the relatively small number of cannabis users in the study.

Bottom line: cannabis may lower a woman's chances of conceiving. If you're trying to get pregnant, consider laying off weed for now and keeping an eye on new research that brings more clarity to this important reproductive health question.