Citing concerns about the accuracy of preimplantation genetic diagnosis, the method many practitioners use to pick the healthiest embryos during IVF, UF researchers set out to study the procedure. Their work, described during a recent meeting of the American Society of Reproductive Medicine, reveals the technique is actually highly reliable. But because there is a slim chance a genetic abnormality can cause doctors to misdiagnose embryos, some concerns still need to be addressed, the researchers said.

Preimplantation genetic diagnosis has been used for more than a decade to screen embryos for hereditary diseases such as Down syndrome and other abnormalities. To do this, one cell from an eight-cell embryo is extracted and examined for chromosomal defects.

However, as many as half these embryos spawn cells with different genetic information as they divide, giving doctors an inaccurate idea of how the embryo will continue to develop, said Larissa Kovalinskaia, M.S., a UF research associate with the College of Medicine's IVF program. While many embryos with this abnormality - called chromosomal mosaicism - stop developing early, some go on to be born. Because these embryos' cells contain different sets of chromosomes, doctors cannot always accurately screen them for genetic diseases, Kovalinskaia said.

"As more data were coming out, saying that as many as 50 percent of (IVF) embryos were mosaic, we started worrying about the accuracy of preimplantation genetic diagnosis," she said. "When you take one cell, does it represent the entire embryo? What we've shown is that we can rely on PGD."

UF researchers estimate less than 3 percent of healthy embryos are dis
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Contact: April Frawley Birdwell
afrawley@vpha.health.ufl.edu
352-273-5817
University of Florida
20-Dec-2005