A panel under the Japan Society of Obstetrics and Gynecology has approved a plan to conduct clinical research in which eggs fertilized in vitro will be checked for possible abnormalities by examining their chromosomes.

The research is aimed at studying whether returning eggs found to have no abnormalities to the womb will help avoid miscarriages. But critics say the method poses ethical questions as it could lead to the exclusion of a broad range of chromosomal abnormalities, including Down syndrome.

According to sources, the society's ethics committee has discussed a method called "array CGH" that can effectively check all of a human cell's chromosomes, which are the structures that hold genes and are typically grouped into 23 pairs.

The plan, which still requires the society's final approval, says the clinical research would begin in April and continue for three years.

If the study is approved, the chromosomes of fertilized eggs will be analyzed at Keio University, Nagoya City University and other institutions.

To date, the society has conducted fertilized egg diagnoses on a case-by-case basis, limiting the practice to cases in which a woman could deliver a child with a serious genetic illness, or when a woman has experienced repeated miscarriages because of chromosomal abnormalities.

More than 350 cases have been approved since the first such diagnosis was conducted in 2004.

In Japan, a new type of prenatal diagnosis, in which chromosomal abnormalities of a fetus can be checked using the pregnant woman's blood, began in April of last year.

About 7,700 women have undergone the tests, of whom 113 had abortions.