Comprehensive Chromosomal Screening (CCS)

 

IVF with CCS

CCS (comprehensive chromosomal screening) is a breakthrough technology that can increase the success rate of IVF up to 70% in even high risk patients.

CCS is a screening technique that is used with IVF to determine if an embryo contains a normal number of chromosomes. Healthy embryos should have 23 pairs of chromosomes. CCS is often also referred to as preimplantation genetic screening (PGS).

We recommend CCS to anyone having IVF but you might be particular interested if you have had repeated miscarriages, failed IVF, or are over 36 years of age.

How Is CCS Different from Traditional IVF?

Typically, in IVF embryos are graded by their appearance. However, this is a bit like “judging a book by its cover” as there is no way of determining whether an embryo has the right number of chromosomes based on its appearance. CCS is a technique that lets us verify that embryos appearing normal are in fact chromosomally normal.

What Are the Advantages of CCS ?

Selecting embryos that have been identified as normal with CCS can:

  • Increase pregnancy rates to 70% or more.
  • Reduce miscarriages rates to 5%-7%.
  • Minimize risks for chromosomal anomalies such as Down syndrome.
  • Allow chromosomally normal embryos to be frozen for future use.

What Are the Possible Outcomes of Embryos Tested by CCS ?

Results will be relayed to you by a telephone call from one of the clinic doctors or genetic counsellors. Details of the results for each embryo tested will be reviewed with you at this time and may include the following outcomes:

  • Normal chromosome number (euploid) : These embryos have 46 chromosomes in each cell and are the best candidates for a successful transfer.
  • Abnormal chromosome number (also called aneuploidy): These embryos have missing or extra whole or partial chromosomes in every cell and are likely to result in a miscarriage, failed transfer or a baby with a chromosomal disorder.
  • Degraded DNA or No Diagnosis: Results were unable to be obtained due to several possible issues. Embryo rebiopsy is offered.
  • Mosaicism: Embryos with a mosaic finding have some cells with a normal number of chromosomes (46) and some cells with extra or missing whole or partial chromosomes. This result is less clear than the first two options.
    • If a normal euploid embryo is present, a mosaic embryo will not be transferred as they carry a high rate of failed implantation and often end in early pregnancy loss (70%)
    • Mosaic embryos with chromosomal abnormalities associated with known genetic syndromes, such as trisomy 21,13,18, would not be considered for transfer
    • Transferring any mosaic embryo is associated with uncertainty as to the possible health of the child
    • Consideration to the disposition of mosaic embryos is undertaken in consultation with your physician and after genetic counselling

What If an Embryo Has an Abnormal Number of Chromosomes?

If an embryo has too few or too many of any particular chromosomes, it could:

  • Fail to implant.
  • Result in a miscarriage.
  • Lead to offspring affected by conditions such as Down syndrome.

The probabilities of these outcomes increase with maternal age.

What are the steps in CCS?

Embryos created by IVF are grown up to the blastocyst stage (5 or 6 days after fertilization). A sample of about 5-10 cells are biopsied from the portion of the embryo destined to form the placenta. The inner cell mass, which will eventually form the baby, is left unharmed.

The embryos are frozen and remain at Olive, but cells are sent to a laboratory for genetic testing. The number of chromosomes for each embryo is analyzed with a technique called array comparative genomic hybridization (aCGH).

What does CCS involve?
 

What Determines the Chances of Finding a Normal Embryo?

  1. The number one factor is a woman’s age. The younger the patient, the greater the chance that any individual embryo will be normal. About 80% of the chromosomal problems in the embryo are due to egg quality, which significantly deteriorates with age. The chances of a chromosomally normal embryo at various ages is:
    • 35 years old = 65 %
    • 42 years old =25%
  2. The second factor is the number of embryos available for biopsy. Most eggs will not lead to embryos that will survive to the blastocyst stage. The more embryos are available for testing, the more likely it is to find at least one that is normal. This is also related to age, since younger patients also tend to have more eggs retrieved, and subsequently more embryos available for biopsy.

Could All My Embryos Be Abnormal?

Sometimes all of the embryos tested are abnormal, leaving nothing available for transfer. While this is a very disappointing possibility, CCS is of value, since it potentially avoids implantation of an unhealthy embryo that could lead to miscarriage or chromosomal disorders in the baby.

What Are Some of the Limitations of CCS?

Research shows that by far the most common reason for pregnancy failure and miscarriage is an abnormal number of chromosomes in an embryo, which can be identified by CCS.

However, even embryos that are identified as normal by CCS do not guarantee a pregnancy or a healthy live birth.

Other important determinants of the health of the embryo that CCS can’t identify include:

  • Genetic conditions, such as cystic fibrosis.
  • Non-genetically determined conditions, such as autism.
  • Problems with the uterus that may prevent implantation.

Is CCS More Expensive than Regular IVF?

As CCS requires several additional steps compared to traditional IVF, there is an increase in cost. However, many experts believe that the overall advantages of CCS, such as improved pregnancy rates and decreased miscarriage rates, will result in an overall cost benefit.

The Olive finance department will discuss the expenses in detail. 

Book an appointment to learn more about CCS is an option

Get started at
Olive Fertility Centre

Fertility Services