Researchers at the University of North Carolina at Chapel Hill
are working on a project they hope will provide a simpler method
for male contraception. By exposing rat testicles to two
15-minute doses of ultrasound, they found that sperm counts
dropped to levels that are usually associated with infertility
in humans. The research was performed with the help of a grant
from The Bill and Melinda Gates Foundation, but is still far
from ready for prime time. It’s still unclear, for example, if
the effects are reversible, and whether there might be long-term
damage from repeated doses. In addition, sperm must be killed
completely rather than simply damaged, since damaged sperm could
produce a child with birth defects. "The last thing we want,”
Allan Pacey, from the University of Sheffield told BBC News, “is
a lingering damage to sperm."