A new study in mice reveals that a body chemical related to a compound in marijuana may complicate pregnancy if present in excessive amounts. The findings could have implications for pregnant women, who may put their embryos at risk by getting high.
The psychoactive compound in marijuana, THC, is similar to some of the body's own signaling molecules, called endocannabinoids. These molecules mediate their effects by binding to two proteins, called CB1 and CB2. The exact role played by these endocannabinoids in reproduction is unclear, but high levels are associated with miscarriage in women.
To clarify this role, a team led by Sudhansu Dey, a reproductive and developmental biologist at Vanderbilt University Medical Center in Nashville, Tennessee, examined mice lacking the CB1 and CB2 genes. Reporting in the 19 September issue of Nature Medicine, the team discovered that embryos often get stuck in the oviducts of these mice and can't reach the uterus. The same problem occurred when the team injected booster shots of a synthetic endocannabinoid. Because the CB1 protein is only found in the muscles of the oviducts, the researchers conclude that endocannabinoids help coordinate the transport of embryos to the uterus.
The study shows that embryo transport is dependent on chemical "fine-tuning," says Vincenzo Di Marzo, a reproductive biologist at the National Institute of Molecular Biology in Naples, Italy. Dey warns that women who use marijuana could be at risk for ectopic pregnancy--the development of an embryo attached to the fallopian tube rather than the uterus--which can threaten the lives of both baby and mother. But Di Marzo cautions that "the general picture in humans might be dramatically different," and it is not yet known whether THC reaches dangerous concentrations in the fallopian tubes of women using marijuana.