Alison Murdoch, MD, Head of the Department of Reproductive Medicine at Newcastle Fertility Centre, was quoted in an Oct. 13, 2003 BBC article:
Male fertility is quite complicated. The partners of men with low sperm counts can sometimes achieve pregnancy, and it is only when men produce very, very small amounts of sperm that they can be considered infertile.'
Charles Ksir, PhD, Professor of Psychology at the University of Wyoming, and Oakley Ray, PhD, Emeritus Professor of Psychology and Pharmacology at Vanderbilt University, wrote in their 2004 textbook Drugs, Society and Human Behavior:
Heavy marijuana smoking can decrease testosterone levels in men, although the levels are still within the normal range and the significance of those decreases in not known.
There have been reports of diminished sperm counts and abnormal sperm structure in heavy marijuana users, but again the clinical significance of these reports is not clear.
Herbert Schuel, PhD, Professor Emeritus of Anatomy and Cell Biology at the University of Buffalo, and Lani Burkman, PhD, Assistant Professor of Gynecology and Obstetrics at the University of Buffalo, et al., presented their study at the 2003 annual meeting of the American Society of Reproductive Medicine, stating:
Marijuana smokers appear to have impaired fertility potential.
Smoking men have reduced semen volume and total sperm number. Seminal sperm from MJ men express abnormally high hyperactivated mobility which persists after a wash and swim-up. These sperm may burn out quickly and reduce fertility.
We note that women smoking marijuana will have elevated THC throughout their reproductive tract, thus affecting sperm in the cervix, uterus and oviduct.