Genetic testing of embryos has been around for more than a decade, but its use has soared in recent years as methods have improved and more disease-causing genes have been discovered. The in vitro fertilization and testing are expensive — typically about $20,000 — but they make it possible for couples to ensure that their children will not inherit a faulty gene and to avoid the difficult choice of whether to abort a pregnancy if testing of a fetus detects a genetic problem.

But the procedure also raises unsettling ethical questions that trouble advocates for the disabled and have left some doctors struggling with what they should tell their patients. When are prospective parents justified in discarding embryos? Is it acceptable, for example, for diseases like GSS, that develop in adulthood? What if a gene only increases the risk of a disease? And should people be able to use it to pick whether they have a boy or girl? A recent international survey found that 2 percent of more than 27,000 uses of preimplantation diagnosis were made to choose a child’s sex.

In the United States, there are no regulations that limit the method’s use. The Society for Assisted Reproductive Technology, whose members provide preimplantation diagnosis, says it is “ethically justified” to prevent serious adult diseases for which “no safe, effective interventions are available.” The method is “ethically allowed” for conditions “of lesser severity” or for which the gene increases risk but does not guarantee a disease.

There is no question that the method’s use is increasing rapidly, though no group collects comprehensive data, said Dr. Joe Leigh Simpson, vice president for research at the March of Dimes and past president of the American Society for Reproductive Medicine.

The center in Chicago that tested the Kalinskys’ embryos for the GSS gene, the Reproductive Genetics Institute, has tested embryos from more than 2,500 couples and sought to identify 425 gene mutations. The institute’s caseload has risen 40 percent in just the past two years, according to its director, Svetlana Rechitsky, an author of the new paper on the Kalinskys’ case.