Tech advances bode well for prenatal genetic Dx. (Limits to Applicability).

NEW YORK -- Over the next 10 years, expect to see major technologic advances in both intrauterine diagnostic imaging and prenatal genetic testing.

But exciting as they are, none of these advances will likely deliver your patients' greatest desire, Dr. Stephen Brown said at an ob.gyn. symposium sponsored by Columbia University and the Sloane Hospital for Women.

"What they want is to reduce their chances, hopefully to zero, of having a child that will have a terrible life either hopelessly encumbered by physical abnormalities or hopelessly mentally retarded. Despite the many advances made, and anticipating those to come, we are very limited in our ability to offer patients what they really most want," said Dr. Brown of the department of ob.gyn. at Columbia University.

Techniques like fetal MRI, three-dimensional ultrasound, subtelomeric fluorescence in-situ hybridization (FISH), and comparative genomic hybridization (CGH) have the potential to revolutionize in utero detection of congenital anomalies and genetic disorders, including many rare ones. But there are still many other anomalies that would still be undetectable in utero. And the population dynamics of screening, not to mention the cost and the ethical concerns, will limit the applicability of these tests.

Even if the new techniques could be broadly implemented, the ability to treat these disorders will still lag far behind the ability to detect them. "Our ability to fulfill the promise of prenatal diagnosis will still be quite limited," Dr. Brown said.

Still, the new technologies will have their place, and they are already becoming part of prenatal care in many centers. Dr. Brown predicted that fetal MRI will have an increasingly important role. At Columbia University, where he practices, fetal MRI is already being used to assess cases in which sonography has shown a probable structural abnormality that needs further clarification.

Fetal MRI produces dramatic pictures and enough fine detail to characterize structural abnormalities. The big problem is that it is still quite expensive, and the machinery is still too cumbersome to use routinely.