The Fingerprints of Embryos

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"In terms of doing sound science and figuring out what parameters are important to look at, no matter what technique you're using, you have to have fingerprinting," says Boston IVF medical director Michael Alper. (Alper was not involved in the fingerprinting study.)

In addition to piloting the fingerprinting technique, the Monash University study investigated one possible approach to sorting embryos by viability. Using extracted cells, the researchers compared the expression levels of some 45,000 genes between viable and nonviable embryos. In this case, they didn't use the fingerprinting technique; because they could only extract a small number of cells, they could not perform both comprehensive gene-expression analysis and DNA fingerprinting on a single blastocyst. Instead, they pooled cells from viable embryos from women in whom all transferred blastocysts developed into babies, and from nonviable embryos from women who did not become pregnant but had no known uterine deficiencies.

"We felt that embryos that were capable of implantation and growing through to term would have a unique gene-expression profile," says Gayle Jones, a coauthor of the study. More than 7,000 genes differed between viable and nonviable embryos, although the findings are still very preliminary. Ultimately, the researchers hope to narrow down this pool to a handful of markers that could identify those embryos most likely to succeed.

Biopsied blastocyst cells could be tested for these markers in a fast, straightforward procedure. "Then you could decide which embryos you would transfer--which would be the most viable," says David Cram, also a coauthor of the research. And because this smaller-scale analysis would require less genetic starting material, it could be paired with DNA fingerprinting to validate its predictive power.

The study's authors did not observe any negative effects of the blastocyst biopsy, but Marcelle Cedars, director of reproductive endocrinology and infertility at UCSF Medical Center, cautions that much is still unknown about the procedure and that further studies are needed to ensure its safety. Even if the biopsy itself proves harmless, growing the embryo in a dish for six days may be detrimental to development; traditionally, embryos are implanted sooner.

Cedars emphasizes the need to develop less invasive techniques in which embryo biopsy is unnecessary. For now, the DNA fingerprinting approach may prove useful in refining those techniques.

Regardless of their differing approaches, all these research efforts share a common ambition. "We're hoping that this technique will ultimately eliminate multiple pregnancies" associated with IVF, says Jones.

"The goal is no longer just getting a woman pregnant," says Cedars, "but really trying to have a healthy singleton birth."