The parents of a four-year-old Oregon girl with Down syndrome are suing Legacy Health in Portland because they say doctors misdiagnosed their daughter as not having the condition during a prenatal screening.

As a result of doctors' reassurances, according to KATU, the parents decided to continue the pregnancy.  They are suing for $7 million, an amount they say will pay for the girl's care for life.

Court documents were not immediately available, so it's unclear what type of genetic testing the couple underwent.  Genetic counselors say there are different types of screening options, including amniocentesis, chorionic villus sampling, and an ultrasound combined with blood testing.

A blood test with an ultrasound will only predict the risk of developing Down syndrome or other genetic abnormalities, said Virginia Carver, a prenatal genetic counselor at the University of Miami's Miller School of Medicine.

Amniocentesis will determine whether or not a child has Down syndrome and is considered the "gold standard" of testing, Carver said.  That test is typically about 99 percent accurate.

"But even the most accurate test isn't 100 percent accurate," she said.  "There is a small percentage of chance that the testing might not be correct because of human error."

Neither the hospital nor the couple would comment on the case, which is now being heard in a Multnomah County court.