IVF Embryo Screening: Pregnancy Boost?
Researchers Say Technique Lowers Pregnancy Chances for Women Having in Vitro Fertilization
July 5, 2007 -- Screening the embryos of an older woman undergoing in vitro
fertilization (IVF) for genetic defects -- a procedure known as preimplantation
genetic screening -- does not boost her chances of pregnancy and appears to
worsen her chances, Dutch researchers say.
But soon after the study was published in the July 5 issue of The New
England Journal of Medicine, it was criticized by some reproductive
technology experts, who say the researchers' scientific techniques weren't up
Preimplantation embryo screening is offered routinely to "older"
women ages 35 and up at some IVF centers. In the screening technique, which
costs about $3,000 to $5,000, a single cell is aspirated from each embryo to
check for chromosomal abnormalities. The embryo isn't transferred if
abnormalities are present. The screening technique evolved as a logical
extension of preimplantation genetic diagnosis, offered to couples with a known
But the new Dutch study shows that pregnancy rates were lower in the women
who got the test. While 25% of those who got the test got pregnant, 37% of
those who didn't get it became pregnant.
"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," says researcher Sebastiaan
Mastenbroek, MSc, a PhD student at the Center For Reproductive Medicine at the
Academic Medical Center in Amsterdam. Based on the new study results, he says,
"PGS is not the best option for these women. A regular IVF treatment
without PGS provides them with a higher chance of pregnancy."
In the study, Mastenbroek and colleagues evaluated 408 women undergoing IVF
at several Dutch centers from May 2003 through November 2005. They assigned 206
to the genetic screening group and 202 to a group that not get the
Besides a lower pregnancy rate, those who got the embryo screening also had
a lower live-birth rate --24% vs. 35%, the researchers found.
Criticism of the Study
Drawing conclusions from the Dutch study would be premature, critics
say. They found fault with the research for a number of
"This research team is inexperienced," says Santiago Munne, PhD, a
member of the board of directors for the Preimplantation Genetic Diagnosis
International Society, a Chicago-based organization that coordinated research,
education, and training in the technique.
Munne and other critics say that inexperience affected the results. For
instance, 20% of the embryos tested came up with "undetermined"
results, with the researchers unable to term them normal or abnormal.
"Experienced centers typically have a 5% indeterminate rate," Munne
The undiagnosed embryos were transferred to the women, resulting in an
implantation rate of 6% compared with the higher 14.7% implantation rate in the
group of patients whose embryos did not have biopsies, he says.