Reproduction in Humans According to a study conducted by researchers at the National Institutes of Health, women who use marijuana may have a more difficult time conceiving a child than women who do not use marijuana. Marijuana use among the women’s partners was not investigated, which could have influenced conception rates. Sunni L. Mumford, Ph.D., of the Epidemiology Branch at the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development, led the team. The research was published in the journal Human Reproduction.
The women were part of a larger group of women who were attempting to conceive after one or two previous miscarriages. Women who reported using cannabis products—marijuana or hashish—in the weeks preceding pregnancy, or who had positive urine tests for cannabis use, were approximately 40% less likely to conceive per monthly cycle than women who did not use cannabis. Although the findings suggest that cannabis may affect women’s fertility, the authors cautioned that they should be interpreted with caution because the study only included a small number of cannabis users. However, the authors state that their findings suggest that women who are trying to conceive should use cannabis with caution until more conclusive evidence is available.
The researchers examined data from a larger study of over 1,200 women ages 18 to 40 who had one or two miscarriages. The women took part in the study for up to six monthly cycles while attempting to conceive and for the duration of the pregnancy if conception occurred. Following enrollment in the study, the women completed a questionnaire in which they were asked if they had used marijuana, pot, or hashish in the previous 12 months, with responses ranging from never, rarely, occasionally, sometimes, frequently, to daily. Each woman also provided urine samples for analysis when she first entered the study, six months later if she did not conceive, and at the time of a positive pregnancy test if she did conceive.
For each monthly cycle, women who had used cannabis while trying to conceive were 41% less likely to conceive than non-users. Similarly, a smaller proportion of cannabis users than non-users became pregnant during the study—42% versus 66%. The authors found no differences in miscarriage rates between users and non-users who had achieved pregnancy.
The authors noted that, compared to non-users, cannabis users also had differences in reproductive hormones involved in ovulation. These differences could potentially have influenced their likelihood of conception. Specifically, users had higher levels of luteinizing hormone and a higher proportion of luteinizing hormone to follicle stimulating hormone.
The authors also mentioned that animal studies had revealed that cannabis use could alter the uterine lining, making it less likely that an embryo would implant and establish a pregnancy. Women trying to conceive should be aware that cannabis may have an effect on their pregnancy chances until more research is available, according to the authors.