Although media reports emphasize the accuracy of a new noninvasive prenatal screening test, raising expectations among expectant mothers, it does not definitively diagnose three types of chromosomal abnormalities, including Down syndrome, warned Haruhiko Sago, head of the Center for Maternal-Fetal and Neonatal Medicine at the National Center for Child Health and Development.

After months of postponement and discussions by medical experts, the Japan Society of Obstetrics and Gynecology released guidelines in early March to begin clinical trials on the test at limited medical institutions as early as April.

“It is not a definitive but yet a very high-performance test that can be used to avoid invasive tests such as amniocentesis. But this is not a test for all pregnant women,” said Sago.

The NCCHD is one of around 15 hospitals nationwide that is ready to start the test. But media reports that say it has a 99.1 percent accuracy rate, as claimed by its U.S.-based developer, Sequenom Inc., have already caused misunderstanding.

The 99.1 percent detection rate is based on blood samples from women already at high risk of carrying babies with Down syndrome, including those who have a family member with the disorder. Sago, an expert on prenatal diagnosis, explained that the percentage drops to 79.9 percent when testing a group of 35-year-old women, whose risk is estimated to be 1 in 250.

For this reason, medical experts agree that even with the introduction of this new test, the ultimate diagnosis can only be made through the two invasive procedures — chorionic villus sampling or amniocentesis, both of which require that long needles be inserted into the uterus and could cause a miscarriage.

“It was inevitable that this test would come to Japan someday, but it could cause a lot of harm if introduced irresponsibly,” Sago said. “We aren’t promoting this test — we are saying that if it is going to be introduced, we need a firm set of rules.”

The JSOG guidelines specify that only pregnant women of “advanced” age, generally considered 35 and older, or those found at risk of carrying babies with such abnormalities in earlier exams, including sonograms, or women who have previously given birth to babies with such defects, can take the test.

Of the 1,050,698 babies born in 2011, 259,523, or about 25 percent, were born to women 35 or older, according to the health ministry. Medical research has also shown that the older the mother, the higher the risk the fetus will have Down syndrome.

The sheer volume of calls to the NCCHD last fall from pregnant women seeking the test — several hundred a day — means it is extremely likely that some, if not many, will not be able to take it.

“The test is in its trial period because we still don’t know if introducing this test is truly the right thing to do on an individual and social level,” Sago said. “This is a test that is not for life-or-death emergencies — prenatal screenings need to be separated from such cases. There will be women who will not be able to take the test, but I think that is unavoidable.”

Public opinion has been divided, with some calling for stricter rules or prohibiting the test altogether, while others say the JSOG guidelines are too strict, mainly because of the underlying ethical concerns over the likely increase in abortions.

Health ministry data show there were 202,106 abortions performed in 2011. Sago pointed out that most of these had nothing to do with abnormalities.

The doctor, however, added that the center’s data show that about 80 percent of pregnant women opt for abortions if abnormalities turn up in prenatal diagnoses.

“Most women choose to abort their babies because of unwanted pregnancies or for other social reasons. We need to consider whether that should be allowed as well if we are going to talk about screening babies because of abnormalities,” Sago said.

Yearlong clinical studies at the NCCHD and other hospitals will focus on what sort of genetic counseling should be provided for the new blood test. Those interested should talk to doctors at the facilities that are conducting the tests and go through thorough genetic counseling that will include the scientific explanation of the abnormalities and what sort of test it is before deciding whether to take it.

The test, which is not covered by insurance, costs about ¥200,000.

As the medical community struggled to come up with a firm set of rules, a private company entered the picture by offering to send pregnant women to the U.S. to be tested for ¥350,000, excluding travel expenses. This commercial move triggered outrage among doctors as well as the Japan Down Syndrome Society.

“It was going to happen sooner or later, but luckily, no one in the medical field offered to support the company. I think that Japanese doctors maintained their moral dignity by not cooperating,” Sago said, adding that strict rules need to be implemented also to prevent such businesses from expanding.

Although clinical studies are set to begin next month, medical experts have indicated that another round of discussions will be necessary before the blood test is officially introduced in Japan, which has long treated prenatal diagnosis as a taboo, given its sensitive nature.

When the prenatal triple marker blood test was introduced in the 1990s, the health ministry actually issued a statement saying that doctors didn’t need to actively inform pregnant women about it. This blood test is one of the current noninvasive procedures that gives the odds of having a baby with Down syndrome, trisomy 18 or an open neural tube defect, but is a source of concern for its false positives.

Sago noted that one positive step triggered by the controversial test is that Japan was finally beginning to hold open discussions on prenatal diagnosis.

“Before, prenatal screening tests were kept under the radar to prevent many people from taking them. . . . But we’ve seen some progress this time because we are trying to move forward and establish rules,” Sago said. “This, however, doesn’t mean we are promoting the screening. We are just trying to bring these issues out into the open so that everyone can think about it.”

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