Cannabis link to risk of miscarriage
London, (GUARDIAN NEWS SERVICE): Women who smoke cannabis in the early stages of pregnancy could risk miscarriage or an ectopic pregnancy, according to a study. Experiments on mice showed that embryos in females given the drug during pregnancy were more likely to develop abnormally and not make it to the uterus. THC, thechemical in cannabis that gives the high, alters the balance of naturalsignalling molecules in the reproductive systems that govern developmentand implantation of the embryo in the womb.
``This raises concern,'' said Sudhansu Dey at the Vanderbilt UniversityMedical Centre in Nashville. If the same was true in humans then smokingcannabis might mean ``that pre-implantation embryo development will beabnormal and that the embryo might get trapped in the oviduct instead ofgoing to the uterus'', he said.
THC (or tetrahydrocannabinol) affects the system because it ischemically similar to signalling molecules in the body called cannabinoids.One of these, anandamide, controls development of the embryo by binding toreceptors on it. The level of anandamide in the reproductive system iscrucial for normal development.
But if THC swamps the system, for example in a cannabis smoker, itdisrupts this fine control.
To show this effect the team set up pumps which continuously injectednine pregnant mice with THC. The researchers later killed the mice andfound that the embryos in all of them had been held up in the oviduct, thetube linking the ovary to the uterus. This is the equivalent of an ectopicpregnancy in humans. In mice not exposed to THC the embryos proceeded tothe womb normally. The embryos in THC-treated mice also had more cellabnormalities, suggesting developmental problems that would lead tomiscarriage. The results are reported in the Journal of ClinicalInvestigation.
The results echo research on tobacco smokers, showing that they are moreprone to ectopic pregnancies. Experiments on hamsters have shown thatnicotine and tobacco smoke prevent normal transport of embryos to theuterus.
Men do not escape either. Previous research has found that cannabissmokers produce less semen, containing fewer sperm. THC binding tocannabinoid receptors on sperm can prevent binding with eggs. Professor Deyalso points out that his findings suggest problems for obesity drugs whichaffect the cannabinoid system. Because these can bind to the same chemicalreceptors in the body as its own cannabinoids, he worries that they mayhave the unintended consequence of harming a woman's fertility.
Sci. & Tech.