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Finding the Right Embryo to Implant

A quick and easy technique for screening embryos in IVF procedures could lead to an improved chance of pregnancy.
March 28, 2007

Nearly 100,000 in vitro fertilization (IVF) procedures are performed in the United States each year. Yet the procedure’s success rate, scientists say, could use a boost. On average, only one in three IVF procedures results in pregnancy. Many women have to undergo repeated trials before having any success. Among successful procedures, nearly one-third result in twins or other multiple pregnancies, presenting a major health risk for both mothers and babies.

Now scientists at Yale University and McGill University have found a noninvasive way to improve IVF’s overall efficiency and decrease the rate of multiple births. By analyzing the fluid surrounding embryos in culture before implantation, the researchers are able to tell which embryos are healthy and viable.

Traditionally, embryologists look for certain characteristics in a healthy embryo. With a microscope, they take stock of how fast an embryo is dividing, the number of cells it has, and its overall shape. However, fertility experts admit that these predictors are far from definitive. “The question is, how much does it tell you?” says David Adamson, incoming president of the American Society for Reproductive Medicine. “Something, but not nearly as much as we’d like to know.”

“Today we just look at embryos, and it’s almost like a beauty contest,” says Yale University’s Emre Seli, assistant professor of obstetrics, gynecology, and reproductive sciences. “The method hasn’t changed since the 1980s, and it’s surprising that there’s no more technology involved in this.”

To improve the chances of a successful pregnancy, doctors usually implant several embryos at a time–a gamble that can result in multiple pregnancies. This forces women to make a choice: abort one or more fetuses, or carry them all to term. Seli and his colleagues say that accurately identifying viable embryos from the start would significantly decrease the likelihood of multiple pregnancies.

“Our hypothesis is, an embryo that is healthy and likely to cause pregnancy has a different metabolism than a nonhealthy embryo,” says Seli. “And this difference may be detected by the fluid in which [the embryos] grow. In the lab, they grow in a single drop, and the embryo breathes into it and eats from it.”

To test its hypothesis, Seli’s team used spectral analysis and proton nuclear magnetic resonance techniques to analyze the fluid surrounding more than 100 different embryos from 34 women. After taking fluid samples on day three after fertilization, researchers identified certain molecules surrounding viable embryos that differed from the molecules found in the fluids present around nonviable embryos. Specifically, Seli detected varying concentrations in lactate, glycine, and alanine, and he established metabolic profiles for healthy versus nonhealthy embryos with 84 percent accuracy–more than double that of conventional methods.

“It’s like a dream come true because you don’t want to harm the embryo,” says Seli. “The most important aspect is that the test will be noninvasive. It will be fast–less than a minute–and machines will be small, therefore it will be very easy to use in an IVF lab.”

To that end, Seli, who is on the science advisory board of Molecular Biometrics, in Chester, NJ, says that this summer the company plans to set up spectral analysis machines to test his molecular profiling technique in IVF centers throughout the United States, Europe, and Japan.

David Grainger, president of the Society for Assisted Reproductive Technology, says that Seli’s results are interesting, but he points out that they’re preliminary. “The research around embryo selection is cutting edge, and the eventual fruits of this labor will allow clinicians to select the best embryo for transfer.”

Others agree that more testing is needed. “This is an interesting way to evaluate embryos,” says Adamson. “Preliminary results give us some cause for optimism and present a case for doing larger follow-up trials to help to answer the question of if this approach will be helpful.”

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