Sperm and Fertility
The shape of a man's sperm is the best gauge of fertility,
according to a recent study in The New England Journal of Medicine.
Researchers from the National Cooperative Reproductive Medicine Network
have found the best sperm structure is an oval head and long straight
tail. Unusually shaped sperm those with very large or small heads,
or tails with twists and coils were not able to fertilize the
egg. The World Health Organization (WHO) publishes standards of normal
semen measurements, but the guidelines on the quantity of quality semen
indicative of fertility have varied throughout the years and have not
proved themselves in thorough testing.
The men in the study were more likely to be infertile if fewer than 9
percent of their sperm were well shaped, while they were most likely
to be fertile if more than 12 percent of their sperm looked normal.
While there is no surefire way to diagnose fertility, these findings
on well-shaped sperm could help standardize the WHO's criteria.
December 2001 Update