Advocates for people with disabilities are troubled by how much faster the science of prenatal testing is advancing than the public discussion of how it ought to be used.

Some bioethicists envision a dystopia where parents who choose to forgo genetic testing are shunned, or their children are denied insurance. Parents and people with disabilities fear they may simply be more lonely. And less money may be devoted to cures and education.

Among the difficult choices facing prospective parents in coming years, genetics researchers say, will be the ability to predict the degree of severity in chromosomal abnormalities like Down syndrome, which can cause mild to moderate retardation.

Abortion, bioethicists fear, could become a kind of “poor man’s gene therapy,” if cost-conscious health insurance companies see it as less expensive than treating a disabled child. Others argue that prenatal testing will be limited to those who can afford it, leaving the poor to grapple with genetic disability and disease.