A fertility clinic in Nagano Prefecture has been using sperm from close relatives, including the fathers of the husbands, to help married couples conceive, resulting in 118 babies born between 1996 and 2013.

While anonymous donors have been the norm in Japan for more than 60 years, using the sperm of close relatives is controversial due to the potential to complicate family relationships.

In all, 110 couples have used the sperm of the husband's father for in vitro fertilization at the Suwa Maternity Clinic. Seventy-nine of the 95 women who became pregnant gave birth.

Seventeen of them gave birth twice, while others gave birth for a third or fourth time, it was learned Sunday.

Yahiro Netsu, the clinic's director, is expected to discuss the outcome of the method at a meeting of the Japan Society of Fertilization and Implantation in Tokyo on Thursday.

Netsu said 146 couples with infertile husbands received sperm from close relatives.

Of them, 110 couples received sperm from the husband's father, 28 from the husband's brothers and eight from other close relatives.

The Japan Society of Obstetrics and Gynecology allows artificial internal fertilization from anonymous donors and external fertilization between married couples. But it is not clear on other cases.

The society has said in the past that using sperm and eggs from close relatives could complicate family relationships and compromise the welfare of children.