Researchers say the new tests might not be reliable enough yet to replace amniocentesis or chorionic villus sampling, two invasive techniques that carry a slight risk of inducing a miscarriage. But they might reduce the number of women who undergo those tests only to find their fetus is normal.

“You will have dramatically fewer procedures,” said Dr. Stephen A. Brown, associate professor of obstetrics and gynecology at the University of Vermont, who has no financial relationship with any of the companies. “It’s a game-changer.”

The first new test, which analyzes fetal DNA in the mother’s blood, is being offered starting Monday by Sequenom, a biotechnology company in San Diego that is trying to put behind it a data-falsifying scandal on a previous Down syndrome test that it had been developing.

The results of a study published online Monday by the journal Genetics in Medicine showed that Sequenom’s new test picked up 98.6 percent of Down syndrome cases. The false-positive rate — when the test incorrectly said that a baby would have Down syndrome — was 0.2 percent.

“It’s better than anything by far that we’ve ever seen in testing for Down syndrome non-invasively,” said Jacob A. Canick, a professor of pathology at Brown University and the senior author of the study.

The test can be used as early as 10 weeks into a pregnancy, though half of the samples tested in the study were from the second trimester, meaning 15 weeks or more.

Another company, Verinata Health of San Carlos, Calif., has said it would introduce a similar test by early 2012. Gene Security Network, based in Redwood City, Calif., hopes to have a test ready later in 2012. Other companies are also at work.

Similar techniques, which use genetic analysis techniques unavailable until a few years ago, are already being used to determine the gender of the fetus and paternity.

Some people worry that use of such tests early will lead to more abortion of fetuses with even minor abnormalities, the wrong sex or an undesired father.

Some relatives of people with Down syndrome are also concerned that the number of people with the condition will decline, leading to diminished support for them. Some relatives say people with Down syndrome can lead fulfilling lives and be a joy to their families.

Down syndrome, in which a person has three copies of chromosome 21 instead of the usual two, is marked by mild to moderate mental retardation, unusual facial characteristics and various health problems.

Most pregnant women now, regardless of their age, undergo preliminary screening using either ultrasound or tests for proteins in the mother’s blood, or both. Those deemed at high risk are then offered an invasive test, in which fetal cells are extracted from the womb.

But the existing screening tests, besides missing cases of Down syndrome, also have a false positive rate as high as 5 percent. The result is that 15 out of 16 women who undergo an invasive test have a normal baby, according to an estimate in the paper discussing Sequenom’s test.

Some researchers said the new tests like Sequenom’s could be offered to women deemed to be at high risk after initial screening. Women who test negative on the new test would have such a low chance of an affected pregnancy that they might feel comfortable skipping the invasive procedure.

However, women who test positive would still be advised to undergo a more definitive invasive test to be absolutely certain before deciding whether to terminate a pregnancy.

“We don’t feel it’s appropriate to act or make decisions or determine completely that there’s an affected or unaffected pregnancy based on the results of this test,” Dr. Canick said.

Sequenom executives also said they hope the test will be used by women who are at high risk but choose not to undergo the invasive tests, in part because they are afraid of the risk of miscarriage.

Marcy Graham, a spokeswoman for Sequenom, said the test, called MaterniT21, would be offered to doctors, not directly to consumers. All samples will be sent to Sequenom’s laboratory for analysis.

She declined to disclose the price, though she said Sequenom hoped insurers would pay $1,500 to $2,000, or roughly as much as for amniocentesis. The company said it expected that insured patients would have to pay no more than $235 out of pocket.

It is not likely that many insurers will cover the test.

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