Study: Cannabis use could affect pregnancy chances

A new study suggests consuming cannabis while trying to conceive could reduce women’s chances of getting pregnant.

Women who use cannabis could have a more difficult time conceiving a child than women who do not, suggests a study by researchers at the National Institutes of Health (NIH). 

The study which appears in Human Reproduction, studied a group of women trying to conceive after one or two prior miscarriages. 

Women who said they had used cannabis products in the weeks before pregnancy, or who had positive urine tests for cannabis use, were around 40 percent less likely to conceive per monthly cycle than those who did not.

Researchers, led by Sunni L Mumford, PhD of the Epidemiology Branch in NIH’s Eunice Kennedy Shriver, National Institute of Child Health and Human Development, analysed data from a broader study of more than 1,200 women ages 18 to 40 with one or two pregnancy losses. 

The women participated in the study for up to six monthly cycles while attempting pregnancy and throughout pregnancy if conception occurred. 

After enrolling in the study, women responded to a questionnaire asking if they had used cannabis in the past 12 months, with responses ranging from never, rarely, occasionally, sometimes, often, to daily. 

Each woman also provided urine samples for analysis when they first entered the study and after six months if they did not conceive or at the time of a positive pregnancy test if they conceived.

A total of 62 women (five percent) either had a positive urine test or responded that they had consumed cannabis before conception.

For each monthly cycle, women who had used cannabis while trying to conceive were 41 percent less likely to conceive than non-users. 

Similarly, a smaller proportion became pregnant during the study — 42 percent versus 66 percent.

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 noted that animal studies had found that cannabis use could alter the lining of the uterus, making it less likely an embryo to implant and establish a pregnancy. 

However, the authors noted that although the findings suggest cannabis could affect women’s fertility, they should be tempered with caution as the study observed a relatively small number of people.

They add that women trying to conceive should exercise caution with cannabis, until more definitive evidence is available and should be aware that cannabis could potentially affect their pregnancy chances.

Cannabis consumption among the women’s partners — which could have influenced conception rates — was not studied.