However, because nuclear magnetic resonance imaging and mass spectrometry are too expensive and complex to perform routinely in fertility labs,Cedars says that she and her colleagues would then need to develop a quick and simple test for commercial use.

Scientists at Molecular Biometrics, a biotech startup in Chester, NJ, are taking a different approach. They use near-infrared spectroscopy to detect specific molecules involved in oxidative stress, which can be an indicator of health in some tissues. Rather than look at single markers, the researchers have developed a specialized algorithm that can detect differences in the molecular profiles of viable and nonviable embryos.

In an ongoing clinical trial, the company is testing the algorithm's ability to reliably predict the outcomes of 1,500 patients who received a single embryo transfer. So far, researchers have analyzed about half of the cases. According to James Posillico, president and CEO of Molecular Biometrics, comparing selection based on morphology (the standard selection method) with his company's metabolomics test showed that the new test is more accurate.

Posillico and his colleagues plan to meet with the U.S. Food and Drug Administration (FDA) next month to finalize details of the clinical trial and to determine if its outcome will provide enough evidence to lead to the approval of the test. "We are looking to enter the international market, including Japan and Australia, by the end of this year or the beginning of next year," says Posillico. "In the U.S., we hope to have FDA approval by this time next year."

If previous screening methods are any indication, it might be difficult to determine just how helpful these kinds of tests are. Fertility experts disagree about whether aneuploidy screening--a genetic test to look for chromosomal abnormalities, performed largely on older women--actually improves rates of successful pregnancies. Clinical studies of this test have yielded mixed results.

If the tests prove successful, scientists say that these approaches might eventually do more than aid in the selection of embryos: they might actually show scientists how to fix damaged ones. "You could have therapeutic interventions to help embryos implant," says Posillico. "Or perhaps put back missing proteins that cause embryos to go bad."