Prenatal genetic testing in Japan

To examine the use of prenatal diagnosis and maternal serum marker tests (MSMTs) from January 1 to December 31, 1997, in Japan.

Questionnaires were sent to medical facilities, which represent about 80% of the facilities providing prenatal diagnosis.

Prenatal diagnosis was performed in 5,748 women, of whom 5,538 (5,516 amniocenteses and 22 chorionic villus sampling; 96.3%) were screened for chromosomal abnormalities. 89.1% (221/248) of those diagnosed to have fetal abnormalities terminated the pregnancy. Written informed consent signed by both the obstetrician and the pregnant woman undergoing prenatal diagnosis was the policy in 76.5% facilities. A total of 14,682 MSMTs were performed: 8,919 were in pregnant women under 34 years of age and 5,763 were in women aged 35 years or older. Follow-up data were obtained in 10,209; 6,918 women under 34 years were tested; of those 448 had a positive result; 349 underwent amniocentesis and trisomy 21 was diagnosed in 9. 3,291 women aged 35 years or older were tested; of those 634 had a positive result; 607 underwent amniocentesis and trisomy 21 was found in 16 cases. Written informed consent before MSMTs was obtained in 34.5% of the facilities.

The data showed that only 4% of pregnant women above age 35 years underwent amniocentesis in Japan, and a small proportion of pregnant women were being offered MSMTs. Prenatal testing should be carried out only on a voluntary basis. For this purpose, women must be adequately informed.