New Test May Spot Which Embryos Stand Greatest Chance of Survival
Measuring mitochondria in cells better predicted success rate with in vitro fertilization, study says
In the 30 years since the discovery of in vitro fertilization, more than 5 million babies have been born worldwide due to the technique. "In any classroom, there's likely to be one or two IVF children among them," Wells said.
But the process is still relatively inefficient. "Only about 30 percent of IVF cycles actually produce a baby," Wells said. "Many patients have to undergo multiple IVF cycles before they finally achieve that much-desired baby."
Researchers decided to look at mitochondria as a possible culprit for unsuccessful implantation. Mitochondria are responsible for creating usable forms of energy for a cell. They also are involved in key cellular processes such as cell signaling, cell differentiation and programmed cell death.
The doctors reviewed the amount of mitochondrial DNA present in 219 embryos produced by 59 couples.
They found that mitochondrial DNA was elevated in the embryos produced by women in their late 30s and 40s, and also was elevated in embryos with the wrong number of chromosomes. The embryos that had the worst chromosomal abnormalities had the highest levels of mitochondrial DNA.
Researchers then implanted embryos that appeared healthy, regardless of their mitochondria levels. "These are embryos we would have high hopes for," Wells said. "They look good under the microscope. They did not have chromosome abnormalities."
However, only half of the implantations produced a baby.
Based on those findings, doctors established a threshold amount of mitochondrial DNA. "Embryos above that level never implant," Wells said. "About 25 percent of embryos that are chromosomally normal but fail to implant have these elevated levels of mitochondrial DNA."
They verified their findings by repeating the test on a second set of embryos using next-generation genetic sequencing. "It appears this is a genuine phenomenon," Wells said.
Chromosome screening is an expensive procedure, costing about $3,000, but Wells said a mitochondria screen could be added to the same procedure without increasing the cost.
"The mitochondrial screen could potentially be a free add-on on top of chromosomal screening," he said, given that both require a physician to take a few cells from the embryo and pass them on to a genetics lab. "Once you've got those cells, you might as well do as much as you can with them."
Wells warned, however, that the screen only sorts the potential viability of embryos. "These kind of tests aren't a magic bullet. They aren't going to make the embryos any more viable," he said. "In some IVF cycles, you're not going to get any viable embryos."