The annual study by the Japan Association of Obstetricians and Gynecologists collected data on births from 330 hospitals nationwide. That data was then analyzed by doctors at the Yokohama City University Hospital who run the Japanese affiliate of the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR).

According to the results, 13.6 babies for every 10,000 were born with Down syndrome in 2011. That is up compared to the 6.3 babies per 10,000 that were born with Down syndrome in 1995.

The study also examined the number of abortions carried out because the fetuses were suspected of having Down syndrome. Using the number of abortions between 1995 and 1999 as a base, that number increased by 1.9 times between 2005 and 2009.

The estimate of the number of babies that would have been born with Down syndrome had the pregnancy not been aborted was 21.8 per 10,000 babies in 2011.

Although the study did not give an actual number, a tally of births taken from 2011 population statistics suggested that about 2,300 babies should have been born with Down syndrome that year. In reality, only about 1,500 Down syndrome babies were born. The difference of 800 may be partly due to abortions.

Over the past 15 years, there has been an increase in prenatal testing, including ultrasound examinations. In April 2013, a new blood test was introduced that could check on chromosomal abnormalities in fetuses.

According to statistics taken over a six-month period, of the 56 women who were informed of fetus abnormalities, about 90 percent chose an abortion.