Doctors at Tottori University Hospital in Yonago, Tottori Prefecture, have conducted in vitro fertilization with sperm taken from an HIV-positive man using, for the fifth time, a technique that reduces the risk of infecting the wife and unborn baby to almost zero, it was learned Monday.

The team of obstetrician-gynecologists headed by Tasuku Harada is the first in Japan to try the method. They have tried the procedure four times on the same couple since May, but none resulted in pregnancy, hospital officials said.

Doctors at Niigata University's medical department have announced a plan to conduct a similar procedure in the near future on a couple in their 30s.

Harada, who is an assistant professor of gynecology, and his team performed the IVF after asking doctors at Keio University medical school in Tokyo to remove the HIV from the sperm of the husband, who is in his 20s.