When multiple embryos are transferred into a woman's uterus during in vitro fertilization (IVF) and a single baby is born, there has previously been no way to know which embryo successfully implanted and developed. Now researchers have harnessed DNA fingerprinting, the same technique used to settle paternity suits and implicate criminals, to match an embryo to the baby it ultimately becomes. This technique may help researchers develop tests to more reliably discriminate between viable embryos and their nonviable siblings.

Currently, doctors select embryos for transfer based on a crude visual inspection under the microscope. But this tactic fails some 50 percent of the time. Consequently, multiple embryos are often transferred at one time, to increase the chances of a successful pregnancy. Multiple births, which put both mother and babies at risk, often result.

"The next big advance in IVF is going to come from our ability to select embryos better," says David Adamson, president of the American Society for Reproductive Medicine, who was not involved in the project. "It will allow us to increase the pregnancy rate and decrease the multiple-pregnancy rate."

In a study published last week in the journal Human Reproduction, researchers at Monash University, in Australia, led by IVF and stem-cell pioneer Alan Trounson, worked with a group of 48 women undergoing IVF. Five days after fertilization, the researchers used a laser to nick the outer coating of each embryo, known at that stage as a blastocyst. The nick allowed the researchers to extract a small number of cells from the layer of the blastocyst that eventually forms the placenta. The following day, each blastocyst was transferred into the woman's uterus.   Read More...