DOCTORS IN the US have started using powerful new DNA tests to screen foetuses for a wider range of genetic abnormalities, spotting more problem pregnancies early but stirring fears that the results will increase abortions as well as confuse and needlessly alarm many couples.
The tests, which use "gene chips" to detect much subtler chromosomal variations than standard prenatal testing, have also triggered complaints that they mark another step toward a society that seeks to weed out aberrations in the quest for the perfect child.
Proponents argue that the tests allow couples to harness the latest molecular technology to target the most devastating genetic syndromes, alleviating their worries in some cases and in others identifying abnormalities soon enough to terminate the pregnancy or prepare to care for an afflicted baby.
But critics say the tests have not been thoroughly validated and threaten to produce a flood of murky, misleading results that will subject emotionally vulnerable couples to needless anxiety, perhaps prompting some to abort healthy pregnancies.
Some worry that the technique could be used to hunt for the rapidly growing list of genetic markers that merely signal an increased risk for cancer, diabetes, mental illness, obesity, addiction and other conditions later in life. Some day, similar tests could perhaps even vet foetuses for traits associated with beauty, personality or intelligence.
"It's a classic Pandora's box," says Leslie Biesecker of the National Human Genome Research Institute. "Like any powerful technology, it solves some problems while at the same time creating new ones. How you use a powerful technology decides whether it's good or bad."
The testing is being introduced at a time when there is already intense debate about wider screening for Down syndrome, which is detected by examining foetal DNA obtained through amniocentesis or chorionic villus sampling. Called comparative genomic hybridisation, the new tests use "microarrays" or gene chips to search for dozens of less common, often more severe syndromes caused by subtle deletions or additions of genetic material that standard genetic analysis misses.
"We can interrogate the foetal genome to identify smaller pieces of DNA that are either added or subtracted, and many of these can cause disease," says Ronald Wapner of Columbia University, who is leading a $3.3 million government-funded study that is starting to evaluate the technology in 4,000 pregnancies.
Many experts say doctors should wait for the outcome of that study before offering the testing widely. But two labs in the study - Baylor College of Medicine in Houston and Signature Genomic Laboratories of Spokane, Washington - are already publicly promoting the service, and a third at Emory University in Atlanta has quietly started doing the tests.
"I believe it's ready for prime time," says Arthur Beaudet, who chairs Baylor's department of molecular and human genetics. "For people who want the best possible prenatal diagnosis and want the maximum information, this is the best option."
The tests, which cost about $1,600 and are not yet covered by insurance, can detect about 150 known genetic disorders that can cause physical deformities, mental retardation and a host of health and behavioural problems, he says.
"Some of these disorders are quite burdensome. They require lifelong nursing care. In some cases these children never walk, never talk, never feed themselves," Beaudet says. "It can have a major impact on the family. People say, 'I wish you had given me the opportunity to know ahead of time. It's really destroyed our lives.'"
While some couples may choose to terminate a pregnancy when they get a bad result, others may decide to have the baby, and knowing the information helps them and their doctors get ready to care for the child. "There are things we want to detect during the pregnancy so we can anticipate the medical problems once the baby is born," says Lisa Shaffer, Signature's president and chief executive. "That way, once they are born, they already have a diagnosis and can get the care they need as soon as possible. That's the biggest advantage."
So far most couples requesting the tests have already had a child with a genetic abnormality, have a family history of a genetic syndrome or are trying to clarify worrisome results from standard screening such as an ultrasound or conventional genetic analysis. But some couples seek the testing because they want as much information as possible.
"The concern could be because of advanced maternal age," Shaffer says. "They might go into a doctor to have amniocentesis and say, 'Is there anything I can do to rule out any chromosomal abnormalities?' And the doctor says, 'Yes, there's this other test.' " - ( Los Angeles Times/ Washington Post)