The parents of a dead boy who had Down syndrome have sued an obstetrician in Hokkaido who mistakenly diagnosed an amniotic fluid test as "normal," people involved in the case said Sunday.

"We lost the opportunity to determine whether to continue with the pregnancy or have an abortion," the parents argued in filing their ¥10 million damages suit with the Hakodate District Court.

According to the complaint, the mother was told by obstetrician Chikara Endo in March 2011 that an ultrasound examination indicated her fetus may have a disorder.

The mother thus underwent the amniotic fluid test to get a definitive diagnosis in mid-April. In early May, when she was 20 weeks pregnant, she was told by Endo that her fetus did not have a chromosomal defect, even though the report from the agency that conducted the test noted that a defect had been confirmed.

The baby died 3½ months after birth from a complication associated with Down syndrome.

Endo, who runs his own clinic, has admitted that he erred.

"I misread the report as its expressions were confusing . . . I apologize for causing suffering to the parents," he said in March.

The mother said she is suing because she doesn't want anyone else to go undergo this kind of ordeal.

"I hope to inform the public that we have suffered due to the mistake of a doctor, so the same incident will never happen again," she said.