Poma Fertility performs preimplantation genetic screening (PGS) the same way we perform PGD but the genetic testing is different. PGS involves determining the total number of chromosomes contained in the embryo. PGS can also be used to determine if the embryo contains chromosomes with translocations (a special type of numerical chromosome disorder).
The most common situations that might benefit from PGS include female reproductive aging or recurrent miscarriages. In both situations, the fertility problem involves a high probability the embryo has the wrong number of chromosomes. If the screen the embryos for the ones that have the normal number of chromosomes and transfer them, then the likelihood of a successful pregnancy should be higher.
One of the most promising values of PGS will be to improve our ability to select the embryo that will create a successful pregnancy. As we improve our selection skill, we can reliably transfer a single embryo and achieve a single baby. Reducing multiple births is one of the highest priority improvements in IVF treatment.
The genetic testing usually requires 24-48 hours to obtain the result depending on the genetic test. Once the genetic results are available then the embryologists match the embryos to the genetics results and they select which embryos are best to transfer back into the woman for pregnancy. The underlying concept is to transfer embryos that have the desired genetic result.
There are two basic forms of PGD: single gene analysis (looking for the absence of specific gene mutations, which cause disease) and aneuploidy analysis (looking for the number of chromosomes).
The techniques used for these tests include PCR (Polymerase Chain Reaction) for single gene analysis, FISH (Fluorescence In Situ Hybridization) or CGH (Comparative Genomic Hybridization).
PGD outcomes are best when there are larger numbers of embryos to work with. This fact is also true of any IVF cycle. The reason is that only about 75% of eggs fertilize normally and become embryos. Then, only about 33% of embryos are high quality and likely to produce a viable pregnancy.
Patients who need PGD for genetic diseases like cystic fibrosis, are usually fertile and easily able to become pregnant without any assistance. Nevertheless, when they undergo IVF for PGD, they are subject to all the same issues facing an infertile couple. Setting realistic expectations allows both physician and patients to be partners in achieving the desired outcome.