New research suggests increases in THC levels are linked with decreases in embryo health and fertilization capability.
Understanding the role marijuana plays in conception and pregnancy isn’t as clear and documented as you’d hope. Relying on scientific research to tell the story often leads to conflicting reports. For example, a 2018 study found habitual cannabis use lowers and alters sperm in men; a 2019 study contradicted those claims, reporting that former and current marijuana users had higher sperm counts than men who had never smoked cannabis.
New preliminary research released by The Endocrine Society adds to this growing body of research. Using animals, scientists discovered that when female eggs were exposed to THC — the psychoactive cannabinoid in marijuana — it inhibited pregnancy and the production of viable embryos. The higher the THC levels, the more it impaired the female eggs, researchers reported.
“Currently, patients seeking infertility treatments are advised against cannabis use, but the scientific evidence backing this statement is weak,” study author Megan Misner said in a statement. “This makes it difficult for physicians to properly advise patients undergoing in vitro fertilization.”
To understand this relationship, cow oocytes (female eggs) received different THC concentrations on level with therapeutic and recreational doses. Researchers then recorded data of the oocytes at critical points in embryonic developments, analyzing how the THC affected maturation. Increases in THC levels resulted in lower quality embryos and lower fertilization capability.
This isn’t the first study to suggest women undergoing fertility treatment should lay off marijuana. Women who used marijuana while receiving treatment with assisted-reproduction technology (ART) were twice as likely to lose a pregnancy as those who didn’t use cannabis. Another study published earlier this year found women who smoked marijuana while pregnant negatively slowed infant growth and development.
However, a study conducted by Boston University researchers surveyed more than 4,000 women who were trying to conceive. Participants stated they were both in stable relationships and not using fertility treatment. According to the results, marijuana use had little to no impact on a couple’s chances of getting pregnant. This was true for both women and men, as male partners were also asked about their cannabis use and over 1,000 men participated.