Photo/Illutration A specialist monitors the condition of an egg fertilized by in-vitro fertilization at a medical facility in Osaka. (Asahi Shimbun file photo)

The Japan Society of Obstetrics and Gynecology, citing clinical trials, has decided to greenlight genetic code screening for in-vitro fertilization (IVF) in the hope it will prove a boon to women who have suffered repeated miscarriages.

The pre-implantation test to check whether fertilized eggs have chromosome abnormalities is a common procedure in Europe and the Unite States, although it remains unclear whether the step is effective in terms of guaranteeing a successful birth.

A JSOG symposium held Oct. 23 decided that such tests could help reduce miscarriages. The body expects to revise its guidance on pre-implantation tests before the end of fiscal 2021.

A fertilized egg that contains abnormal chromosomes can result in the egg becoming dislodged in the uterus or cause miscarriage in early stages of pregnancy, even if the egg transfer to the uterus was performed in textbook fashion, according to experts.

Older women are more susceptible to such complications.

If chromosome abnormalities of fertilized eggs are checked in pre-implantation tests, only those with the normal chromosome number will be transferred to the uterus, thereby lowering the risk of miscarriage under the new guideline.

However, concerns have been raised that such tests are tantamount to selecting a fertilized egg that could lead to screening out any embryo with a disease or disability to create a “super race” of beings.

Until now, the JSOG with the backing of academics had banned the procedure except for individuals with a severe hereditary disorder and women who repeatedly experience miscarriages due either to her or her husband’s chromosome abnormality.

The new guideline is targeted at women who have miscarried twice or more and need to undergo IVF, those who did not become pregnant despite undergoing IVF at least twice and married couples who have a chromosome abnormality on either his or her side.

The JSOG said pre-implantation tests will be made available at medical facilities that have been registered as being able to provide assisted reproduction technologies for more than three years and publish the results of their services on their websites.

The interim report on the clinal trial of 4,348 women by the GSOG showed that 66.2 percent of those who received a transfer of a fertilized egg to the uterus became pregnant.

The ratio of women who miscarried came to 9.9 percent.

The results were a marked improvement from the previous survey in 2019, when the pregnancy rate was 33 percent and the miscarriage rate was 25 percent.

However, the latest report also found that 63.4 percent of women could not receive a fertilized egg that can be transferred to the uterus despite the in-vitro procedure.

“It is not clear whether pre-implantation tests can ultimately contribute to women having a better chance to give birth,” a JSOG representative said.

During the symposium, some participants voiced concerns about the ethical implications for the approved test.

“A new set-up should be put in place to prevent reproductive technologies from being exploited as a mass screening aimed at detecting disorders among embryos,” the Japan Down Syndrome Society said in a statement.

(This story was written by Mirei Jinguji and Kazuya Goto.)