Clinical studies on pre-implantation genetic screening, or PGS, of eggs fertilized in vitro has suggested that the screening can reduce the miscarriage rate, the Japan Society of Obstetrics and Gynecology said.

But the rate of childbirth may remain unchanged after PGS, according to the society.

The research was conducted on 85 women aged between 35 and 42 who have experienced unsuccessful in vitro fertilization three times or more or miscarriages twice or more. After in vitro fertilization, their fertilized eggs were checked for chromosomal abnormalities.

Kuwahara reported on 77 women for whom research data had been compiled.

Of 38 women who had fertilized eggs with no abnormalities transplanted into the womb, 70 percent became pregnant while 10 percent experienced a miscarriage. Kuwahara reported that PGS can reduce miscarriages, with the miscarriage rate for conventional in vitro fertilization estimated at 20 to 30 percent.

On the other hand, half of the 77 women were unable to receive a transplant due to the lack of healthy fertilized eggs. The pregnancy rate of all 77 women stood at 35 percent, little changed from that for conventional in vitro fertilization, according to Kuwahara. None has given birth to a baby and the birthrate may not be higher than for conventional in vitro fertilization, he said.

The society plans to compile a final report after collecting data on women who undergo in vitro fertilization without PGS under the same conditions.

Testing of fertilized eggs has been criticized for the way it selectively sorts them into viable and nonviable categories. The society, therefore, has banned broad-based PGS, while allowing testing only for severe genetic illnesses.

The society, which announced the start of clinical research on PGS in February 2017, is planning to continue the study.