Fertility Treatments & Services Genetic Testing and Diagnosis

About 70% of all failed pregnancies (implantations) are due to chromosomal abnormalities in the fertilized egg (embryo). Pre-Implantation Genetic Diagnosis (PGD) and Pre-Implantation Genetic Screening (PGS) are used to identify which embryos are most likely to result in a healthy pregnancy before they are implanted in the uterus.

PGD tests an embryo for specific inherited diseases (single gene disorders) such as cystic fibrosis and for extra or missing pieces of chromosomes (micro deletions, inversions or translocations). PGD is usually only recommended for couples with known specific genetic abnormalities carried by one or both parents that may be passed on to their offspring.

PGS tests for the presence of any extra or missing whole chromosomes compared to the normal set of 23. PGS works by taking a few cells from each embryo and testing these cells (biopsy).

In the past, the fluorescence in situ hybridization (FISH) method of PGS was more widely used. This method tests for abnormalities in chromosomes including 21, 18, 13, X and Y as abnormalities in these chromosomes can still lead to live births of babies with disorders such as Down Syndrome.

A more advanced and reliable alternative to FISH is Comprehensive Chromosomal Screening (CCS) using the most advanced technologies that tests all chromosomes. We use a technique of CCS called Comparative Genomic Hybridization (CGH) to screen for abnormalities and for sex selection.

Those who benefit from CCS include those where the woman experiences:

  • Infertility
  • Recurrent miscarriage
  • Clinical aneuploidy (Down syndrome) risk
  • Multiple pregnancy risk
  • Sex-linked genetic illness risk
  • Advanced maternal age

After screening for chromosomal abnormalities, healthy embryos can then be selected for implantation or cryopreservation via vitrification (“flash freezing”) or traditional slow-freeze method, depending on the circumstances, for future frozen embryo cycles. Without genetic testing, there is a higher chance of implantation of a chromosomally abnormal embryo, which can result in a miscarriage or baby born with birth defects. Using PGS, we can analyze and select embryos before they are implanted in order to reduce the risk of miscarriage, reduce the chances of having twins due to reduced need to transfer multiple embryos, and to assist with family balancing.


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