Women who use marijuana may have more trouble conceiving than nonusers, according to a study from the U.S. National Institutes of Health (NIH) released this Monday.
The research, published in the scientific journal Human Reproduction, did not look at marijuana use among female partners, which may have affected conception rates, the NIH added in a statement.
Women who reported using products such as marijuana or hash in the weeks leading up to pregnancy or whose urine tests were positive for cannabis were 40% less likely to become pregnant in each monthly cycle than non-users.
While women who used during each monthly cycle while trying to conceive were 41% less likely than women who were not in contact with cannabis.
The difference was greater when the percentage of pregnant women was analyzed: only 42% of those who said they had used cannabis could get pregnant compared to 66% of the non-users.
“Female cannabis users also had differences in the reproductive hormones involved in ovulation. These differences may have affected their chances of conception,” the note said.
The authors further noted that animal studies have shown that cannabis use can alter the lining of the uterus.
The researchers collected this data from a study of more than 1,200 women between the ages of 18 and 40 who had had one or two miscarriages and participated in six-monthly cycles of the study while attempting to conceive or during pregnancy.
A total of 62 women, equal to 5% of all participants, had a positive urine test or said they had used cannabis before conception.
Therefore, the researchers admitted that the number observed was small and recommended caution with cannabis use as long as definitive evidence is available.