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Number of prenatal screening tests in Japan jumps 2.4 times in 10 years


TOKYO -- The number of prenatal tests conducted in Japan to check for serious health issues with the fetus has jumped 2.4 times over a 10-year period from 2006 to 2016, according to an estimate by researchers at the National Center for Child Health and Development and other institutions.

It is estimated that around 70,000 such tests were carried out on fetuses in 2016, meaning a quarter of pregnant women aged 35 or older underwent the tests. The figure was about 29,300 in 2006.

The findings show that the use of prenatal examinations has become more widespread. However, critics have pointed out that this trend may lead to "selection of life," as most people choose abortion when the screening finds abnormalities. The tests check if babies have irregularities in their chromosomes -- structures in cells containing genes that control the design and functions of the human body -- and other health issues.

There is no official data on the number of prenatal diagnoses conducted in Japan or how many facilities carry out the tests. The researchers surveyed facilities which analyze blood samples and other specimens taken from mothers. They then estimated the total number of prenatal tests, such as maternal serum screening tests, non-invasive prenatal genetic testing (NIPT), and tests of the mother's amniotic fluid as well as the villi inside the womb.

According to their estimates, the ratio of pregnant mothers who received such exams was 2.7 percent of the total in 2006, and 15.2 percent among those aged 35 or older. These figures jumped to 7.2 percent and 25.1 percent, respectively, in 2016.

By test type, the number of maternal serum screenings, which test for chromosome abnormalities from the composition of the mother's blood, doubled from about 17,500 in 2006 to about 35,900 in 2016.

Meanwhile, the number of NIPT, which is capable of examining DNA fragments of the fetus in the mother's blood at a high level of accuracy, has been steadily increasing since 2013, when it was introduced on a clinical trial basis by the Japan Society of Obstetrics and Gynecology. As of 2016, the tests registered by a joint research body alone came to 13,628. However, the actual number of NIPT conducted is estimated even higher. This is because it only counts officially registered tests, and not exams carried out by unauthorized facilities, such as those working in tandem with overseas test providers.

The tests of the amniotic fluid and villi in the womb can determine disabilities or diseases the fetus carries with 100 percent precision. However, they pose the risk of triggering a miscarriage because test samples have to be taken from the mother's womb using a syringe. While amniotic fluid tests have increased from 11,703 in 2006 to 18,600 in 2016, the number is declining since the introduction of NIPT. The blood serum test and NIPT are easier to carry out, as only blood samples from the mother are required, but their precision is lower -- an average 89 percent accuracy for NIPT.

As for the number of facilities capable of conducting these prenatal diagnostic tests, the research team estimated that 876 facilities can check amniotic fluid and 1,509 institutions can carry out the maternal serum screening test. The obstetrics and gynecology association is considering revising its guidelines to increase the number of facilities where NIPT can be conducted.

(Japanese original by Norikazu Chiba, Science & Environment News Department)

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