LOS ANGELES -- An increasingly popular procedure that is widely touted as a way to boost birth rates for older women undergoing in vitro fertilization actually reduces births by one-third, Dutch researchers said yesterday.
The finding represents a major setback for pre-implantation genetic diagnosis, which involves removing a single cell from a 3-day-old embryo to look for potential birth defects.
Although only a few thousand procedures are performed each year, researchers estimate the frequency has been growing by as much as 30 percent a year.
"This is not helping people get pregnant," said Dr. Elizabeth Ginsburg, medical director of the in vitro program at Brigham & Women's Hospital in Boston , who was not involved in the research. "Smaller studies have shown similar things."
The technique remains valid for testing for specific genetic defects that the mother or father are known to carry, which is its most common use.
But "this rings the death knell" for the use of the technique for routine screening of older women, said Dr. Richard Scott, founder of Reproductive Medicine Associates, a chain of in vitro centers in the Northeast.
The technique was developed about 17 years ago. It is based on the idea that one cell can be removed for analysis from the eight cells in a 3-day-old embryo and that the remaining seven cells will grow into a healthy infant. If genetic analysis shows an abnormality, the embryo is not implanted.
Although the procedure was designed to look for specific genetic defects, practitioners have been using it to screen older women having difficulty conceiving in the belief that weeding out embryos with abnormalities will increase the success rate of implantation.
To test this, Dr. Sebastiaan Mastenbroek, of the Academic Medical Center in Amsterdam, and his colleagues studied 408 women between ages of 35 and 41. Half were assigned to receive in vitro fertilization with pre-implantation diagnosis and half only in vitro. Each woman went through as many as three fertilization cycles.
Mastenbroek reported at a meeting of the European Society of Human Reproduction and Embryology in Lyon, France, that 24 percent of the women receiving the genetic diagnosis had successful births, compared with 35 percent of the women who did not.
"Our field has tended to accept new technologies without a lot of scrutiny," Ginsburg said. "Clearly, this is one that was overrated."
The results will be published today in the New England Journal of Medicine.