A Japanese medical society on Saturday expelled a member doctor for performing an in vitro fertilization with the eggs of an unmarried woman, a news report said.

The Japan Society of Obstetrics and Gynecology said Yahiro Netsu violated the group's ethical rules by performing the operation, Kyodo News reported. The society could not be reached late Saturday for comment.The report said Netsu conducted an in vitro fertilization for a married couple, using the husband's sperm and the eggs of the woman's unwed sister.

That violated the society's rules against "extra-marital" in vitro fertilization, an operation in which a woman's eggs are fertilized in a laboratory and transferred into the uterus.

Netsu practices gynecology in northern Japan, and the expulsion will not affect his right to work. He announced earlier this week he will leave the society to continue practicing similar fertilizations, Kyodo said.

The ethical rules have come under scrutiny as Japan focuses attention on its rapidly declining birthrate. The Ministry of Health and Welfare is holding a series of hearings this year that will touch on such restrictions.