WEDNESDAY, July 4, 2007 (HealthDay News) -- Routine screening of the embryos of older mothers won't increase their chances of successful pregnancy after in vitro fertilization, and might even have the opposite effect, a new Dutch study suggests.
In the July 5 issue of the New England Journal of Medicine, European researchers report that the live birth rate for older women who had preimplantation screening as part of the in vitro fertilization (IVF) procedure was 24 percent compared to 35 percent in women who had IVF without preimplantation screening.
"Preimplantation genetic screening is meant to increase the chance to achieve a live birth," said Sjoerd Repping, director of the IVF laboratory at the Center for Reproductive Medicine at the Academic Medical Center in Amsterdam. Instead, Repping said, "PGS significantly reduces the chance of an ongoing pregnancy in women of advanced maternal age."
Preimplantation genetic screening is done by removing one or two cells from an embryo before it's implanted in the mother's uterus. Those cells are then tested for certain known abnormalities, such as cystic fibrosis, Huntington's disease and sickle cell anemia. The procedure adds between $3,000 and $5,000 to an IVF attempt, but for people at high risk of transmitting a genetic abnormality, it can help assure a healthy pregnancy.
"Preimplantation genetic diagnosis is not without risk, however," wrote Dr. John Collins from McMaster University in an accompanying editorial. On average, live birth rates are lower after preimplantation screening, according to Collins.
Dr. Jamie Grifo, director of the division of reproductive endocrinology at the New York University School of Medicine, said he believed the act of taking a biopsy from the embryo to remove the cells for genetic testing does reduce the pregnancy rate "to some extent."
But, he added, in certain high-risk women, the benefits of knowing that you're not transmitting a devastating genetic illness to your offspring outweigh the risks of the procedure.
The current study included 408 women between 35 and 41 years old, ages that are considered "advanced" when trying to conceive. Two hundred and six were randomly assigned to the preimplantation genetic screening group and the remainder to a control group receiving standard IVF.
The rates of ongoing pregnancy -- defined as a pregnancy lasting 12 weeks or longer -- was 25 percent in the preimplantation screening group versus 37 percent in the non-screening group. And, live birth rates were 24 percent and 35 percent, respectively.
Repping said that several factors may be responsible for this difference. The first is that the act of taking a biopsy may damage embryos somehow. Another is due to technical limitations of the preimplantation screening -- embryos currently thought to be normal may actually have unknown defects. And, finally, the cell or cells tested may not be representative of the whole embryo.
"Preimplantation genetic screening is an expensive technique that is very frequently offered to women of advanced maternal age under the statement that it will increase pregnancy rates. The fact that the data show that it does not -- on the contrary, it decreases pregnancy rates -- should be included in the counseling of these patients undergoing IVF treatment," said Repping.
Grifo had several concerns about the study, however. One is that the pregnancy rates achieved in the study were lower than those commonly achieved in the United States. "Will these findings hold up in programs that have better pregnancy rates? This is a technique that requires a lot of experience and continued practice," said Grifo, who added that the study did not detail the experience level of the technicians involved in the study.
Additionally, Grifo said that preimplantation screening isn't routinely recommended for older women who don't have a history of genetic disorders or recurrent miscarriages.
One of the best things an older woman who plans on undergoing IVF can do to increase her chances of having a baby, Grifo said, is to make sure she goes to a clinic with lots of experience and higher success rates.
"This is a highly specialized technique that requires a team of experienced people," he explained.
The study was released early Wednesday to coincide with a presentation at the European Society of Human Reproduction and Embryology's annual meeting in Lyon, France.
More information
To learn more about in vitro fertilization, visit the American Society of Reproductive Medicine.
