Using cannabis ‘can lead to miscarriages’
Women risk losing their babies if they smoke cannabis at the time of conception or early in pregnancy, according to a study published yesterday.
Cannabis is the most widely-used illegal drug among women of childbearing age. Scientists studying mice have found that THC, the active ingredient in the drug, can retard embryo development and prevent it from reaching the womb.
The findings suggest that smoking cannabis may lead to miscarriages caused by embryos developing outside the womb, in the fallopian tubes.
Writing in the Journal of Clinical Investigation, the team, led by Dr Haibin Wang and Dr Sudhansu Dey from Vanderbilt University in Nashville, Tennessee, warned: “Our observation of … mice exposed to excessive THC raises concern that the adverse effects of maternal use of marijuana could be seeded very early in pregnancy.”
THC, or tetrahydrocannabinol, binds to two receptors in the brain called CB1 and CB2. Receptors are proteins into which other molecules fit like a key in a lock. Biological processes are triggered when molecules bind on to receptors.
THC activity in the brain leads to the “high” enjoyed by cannabis users. But CB receptors are also found in sperm, eggs and newly-formed embryos.
During early pregnancy, a naturally-occurring molecule called anandamide normally activates these receptors and the team found that anandamide levels are carefully balanced to maintain normal embryonic development.
When pregnant female mice were exposed to THC, the drug had the same effect on the CB1 receptor as anandamide and swamped the finely-tuned signalling system.
The researchers found that this, in turn, led to embryos remaining in the fallopian tubes instead of becoming implanted in the womb as nature intended. “Embryo retention in the fallopian tube is a significant cause of ectopic pregnancy, the incidence of which has markedly increased during the past decade,” they wrote.
Embryos recovered from the treated mice also showed signs of apoptosis – a natural process by which defective cells destroy themselves.
In an accompanying commentary Dr Herbert Schuel from the State University of New York points out that a number of drugs used to suppress appetite or trigger weight-loss also affect anandamide signalling and, therefore, need to be carefully monitored.
Using cannabis ‘can lead to miscarriages’ Women risk losing their babies if they smoke cannabis at the time of conception or early in pregnancy, according to a study published yesterday.