Women who use cannabis may have harder time conceiving

Women who use cannabis may be less likely to conceive than women who do not, according to research published in Human Reproduction.

“The key clinical takeaway is that though there is a general perception of safety, the use of cannabis while trying to become pregnant may be associated with reduced fecundability, based on data combining both urinary metabolites and self-report,” Sunni L. Mumford, PhD, an investigator in the epidemiology branch of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development, told Healio Primary Care. “It is still unknown whether cannabis use influences the risk of pregnancy loss.”

Mumford and colleagues conducted a secondary analysis of a study investigating the impact of preconception use of low-dose aspirin on pregnancy. The study included women aged 18 to 40 years who had a history of pregnancy loss and were recruited from four clinical sites from 2006 through 2012.

The prospective cohort study included women who were followed for up to six menstrual cycles while they were attempting to conceive.

Women completed questionnaires at baseline that included lifestyle, sociodemographic, sociodemographic factors, health and reproductive history. They also completed daily diaries throughout the first two menstrual cycles of follow-up and provided daily urine samples used to measure reproductive hormones or early pregnancy losses.

At baseline, women reported any cannabis use, and urinary THC metabolites were assessed at preconception and in early pregnancy.

A total of 1,228 women were included in the study, 5% of whom had preconception cannabis use based on self-reports and urinary metabolites. Based on urinary metabolites, 1.3% of the women in the study used cannabis during the first 8 weeks of pregnancy.

Mumford and colleagues determined women who used cannabis were 41% less likely to conceive than women who did not (fecundability OR = 0.59; 95% CI, 0.38-0.92).

Additionally, they found that 42% of women who used cannabis prior to conception became pregnant, compared with 66% of women who did not.

They determined that self-reported cannabis use was associated with a 42% reduction in fecundability (FOR = 0.58; 95% CI, 0.35-0.98) and having a urine metabolite measurement indicating cannabis use was associated with a 47% reduction in fecundability (FOR = 0.53, 95% CI, 0.29-0.96), though the association was imprecise after adjusting (aFOR = 0.60; 95% CI, 0.32-1.12).

The results were similar after adjusting for parity, income, employment and stress, and after excluding women who smoked, used alcohol or reported any drug use in the previous year.

The researchers did not identify an association between preconception cannabis use and pregnancy loss.

Mumford and colleagues observed associations between preconception cannabis use and increased incidence of intercourse per menstrual cycle, higher levels of luteinizing hormone, and a higher proportion of luteinizing hormone to follicle stimulating hormone compared with women who did not use cannabis.

“Some evidence suggests that exogenous cannabinoids may inhibit release of GnRH, a key factor involved in ovulatory function, uterine receptivity and implantation, which in turn could have important implications for fecundability and pregnancy loss,” Mumford said.

“Patients and providers should be aware that there are potentially adverse effects of cannabis use while trying to conceive,” she added. “It is unknown whether there is a safe level of cannabis use.”