Have a successful pregnancy and a healthy baby by selecting chromosomally normal embryos
Preimplantation genetic screening (PGS) for aneuploidy is a powerful genetic test that may be performed on embryos during IVF treatment to screen for numerical chromosomal abnormalities. PGS is performed on a small embryo biopsy prior to transfer and identifies which embryos are chromosomally normal. Chromosomally normal embryos are the most likely to develop to term and to be born as a healthy baby. PGS testing helps IVF physicians and patients decide which embryos to transfer.
This procedure allows us to analyze all 24 chromosome types in order to discard the possibility of embryonic aneuploidy before implantation.
PGS offers comprehensive analysis of all 24 chromosome types: the two sex chromosomes (X and Y) and the 22 other non-sex chromosomes. Normally there are 23 pairs of chromosomes in each human cell. A numerical change in the number of chromosomes is called aneuploidy. Aneuploidy is responsible for the vast majority of spontaneous miscarriages and can result in birth defects and mental retardation in live born babies. Most types of aneuploidy are not compatible with life. The most common syndromes caused by non-sex chromosome aneuploidies are Down syndrome, Edwards syndrome, and Patau syndrome. Aneuploidy is usually not inherited and can involve any chromosome; however, the likelihood of embryos to be aneuploid increases with the age of the mother.
The majority of abnormal embryos are indistinguishable from normal embryos when studied using a microscope. Therefore, normal embryo appearance cannot be used to evaluate for chromosome abnormalities. For women in their mid thirties and older, the risk for chromosome abnormalities is significantly higher than for younger women. Women with a history of recurrent miscarriage or recurrent implantation failure, or who have had a prior pregnancy with a chromosome abnormality, or men with abnormal sperm analysis may also create a higher percentage of abnormal embryos.
The main benefits of PGS for chromosome abnormalities include increase in implantation rate, reduction in miscarriage rate, and increase in the chance of delivering a healthy baby:
Increase in implantation rate: Some embryos that are chromosomally abnormal will fail to implant into a woman’s uterus. Therefore, by transferring chromosomally normal embryos, PGS using an array can increase the implantation rate.
Reduction in miscarriage rate: In the general population, 20% of all clinical pregnancies miscarry and about half are chromosomally abnormal. Since PGS evaluates numerical changes in chromosome numbers and large chromosome imbalances, embryos with chromosome abnormalities will not be transferred. Therefore, especially, in high-risk groups, PGS reduces the risk for miscarriage.
Increase in the chance of delivering a healthy baby: Some pregnancies with chromosome abnormalities will result in the birth of a child with multiple serious anomalies. Therefore, PGS can increase the chance of delivering a healthy baby by assisting physicians in identifying chromosomally healthy embryos for transfer. These conditions can also be detected by chorionic villus sampling (CVS) or amniocentesis later during the pregnancy.
Over 50% of spontaneous miscarriages are caused by chromosomal abnormalities. Some birth defects are caused by chromosome abnormalities, and the risks of having a child with a chromosome abnormality increases with maternal age. Couples who are at increased risk for having aneuploidy embryos should consider using PGS testing. These groups of individuals include:
The selection of chromosomally normal embryos in these couples greatly reduces the risk of miscarriage and increases reproductive success.
The rhythm of life has caused more and more women to decide to become mothers later in life when their fertility has been reduced. A woman is born with a certain number of eggs, and her ability have children decreases over her lifetime, in part because the chance of chromosome abnormalities also increases as she ages. Most embryos with an incorrect number of chromosomes fail to implant or miscarry during the first trimester of pregnancy. The decline in fertility is gradual, but many medical providers consider the risks of chromosome abnormalities to be significant at age 35 or older. Chromosome abnormalities in live borns can cause conditions such as Down Syndrome (three copies of chromosome 21 instead of two), Edwards syndrome, and Patau syndrome.
Approximately 50% of spontaneous miscarriages occur in the first trimester because of random (de novo) chromosome abnormalities. PGS studies in these couples have revealed that 65% of embryos are chromosomally abnormal, and in 15% of couples, all embryos are chromosomally abnormal. PGS evaluates all 24 chromosomes to detect any numerical chromosome abnormality.
Sometimes, even when the egg is successfully fertilized and developing normally, it will not be able to implant into the uterus. This is called implantation failure and may occur because of abnormalities of either the uterus or the embryo itself. If chromosomal abnormalities are impacting embryo viability, the selection of chromosomally normal embryos will improve the chances of implantation and ongoing pregnancy. For couples who experience recurrent implantation failure, about 65% of embryos are expected to be abnormal.
Next Generation Sequencing is the “digital” sequence-based alternative to analog techniques for DNA analysis. With its exceptional data and scalability, it allows us to study chromosomes at a level never before possible.
NGS provides a new approach to PGS with advantages including:
1) State-of-the-art technology:
More detailed genetic information can be obtained through the complete genome sequencing of embryos.
2) High resolution:
Possibility to detect segmental aneuploidies on embryos (deletions/duplications).
This technique can be applied using the same approach for different indications such as for translocation and, in the future, also for single gene disorders.
3) High Accuracy rate:
PGS by NGS achieves an accuracy rate of 98%.
4) Improvement in clinical results:
Due to higher dynamic range of NGS technology, increasing the detection capability of mosaicism and segmental abnormalities.
NGS allows a more cost-efficient approach to PGS with frozen embryos.
Taiwan IVF Group offers competitive pricing strategy for PGS by NGS which will allow all patients to afford and benefit from PGS treatment.