LIVINGSTON, NJ--(Marketwire - December 30, 2009) - A new strategy that researchers believe
provides a more comprehensive screening of the entire chromosomal makeup of
an embryo shows tremendous promise in the field of preimplantation genetic
screening (PGS) according to a study published in the December issue of
Fertility and Sterility.
Forty-five infertile couples participated in the study with an average age
of 37.7 years. Using a novel screening approach, researchers biopsied
several cells from embryos five days after fertilization, also known as the
blastocyst stage. The patients underwent comparative genomic hybridization
(CGH) screening, which researchers say allows for a more comprehensive look
at the chromosomal health of the cell.
Results show successful biopsy in close to 100 percent of the embryos using
CGH. Of these embryos, more than half (51.3 percent) were diagnosed as
abnormal. The remaining embryos with normal chromosome counts were
implanted and of the CGH group, 68.9 percent produced a fetus.
Reprogenetics, LLC, in Livingston, New Jersey, performed the genetic
diagnosis. Its president, Santiago Munne, says the CGH screening results
could provide the answers to challenges that IVF researchers have faced for
"One of the greatest challenges currently facing IVF practitioners is how
to reduce the risk of multiple pregnancy while maintaining or improving
pregnancy rates," says Dagan Wells, a senior scientist at Oxford University
and one of the authors of the study. "The research suggests that CGH will
be an extremely useful tool, allowing us to move IVF toward single embryo
transfer." A reduction in the risks of miscarriage and Down syndrome are
also predicted if embryos are screened using CGH.
Traditionally, PGS has been conducted to improve the success rate of in
vitro fertilization (IVF) for women of advanced maternal age and repeat
pregnancy loss. Research has shown that many times IVF fails because a
majority of the embryos that are created in vitro are chromosomally
abnormal. Embryos with a chromosome abnormality have very little chance of
producing a baby. When performing IVF in conjunction with CGH, researchers
are able to detect embryos with a healthy set of chromosomes and make sure
they are given maximum priority for transfer to the womb.
Many IVF laboratories currently perform chromosome screening (PGS) at the
6-10 cell stage (3 days after fertilization). While this technique has been
shown to improve IVF outcomes by some PGD laboratories, such as
Reprogenetics, others have not been able to duplicate these results. This
is, according to another recent publication in the same journal, due to the
use of non-optimized methods, such as poor embryo biopsy technique.
However, regardless of the method used, the standard technique only detects
a fraction of chromosomes and by analyzing a single cell may have an
intrinsic risk of misdiagnosis, which at Reprogenetics is about 6%.
CGH allows researchers to overcome both of these perceived obstacles.
Biopsy is performed at the blastocyst stage, a full two days later than
traditional PGS methods, where several cells can be safely sampled from a
tissue that will not become fetus but placenta (the trophectoderm). As
previous studies have shown, cells sampled during this stage are highly
representative of the remainder of the embryo and thus the errors are
minimized. In addition, CGH allows researchers to screen all chromosomes
"The blastocyst-CGH approach shows enormous promise," states Dr. Wells.
"Despite these encouraging results, we plan to follow up with a randomized
trial to confirm the efficacy of this new procedure."
The CGH technique has been further improved since the submission of this
work for publication, by allowing analyses of day 3 embryos in 24 hours, a
new technique called array CGH.
For more information on Reprogenetics or to find a center trained in the
latest PGS protocol, contact client services at
firstname.lastname@example.org or 973-436-5004.