Normal human body cells contain 23 pairs of chromosomes; 22 pairs of autosomal (or non-sex chromosomes) and one pair of sex chromosomes. A banded karyotype blood test assesses the number and structure of chromosomes within the cells. A normal karyotype reads as 46XX for a female, and 46XY for a male.
What are the types of karyotype problems?
There are many Karyotype abnormalities. The wrong number of chromosomes can present as a genetic syndrome. For example Klinefelter syndrome (where a male has an extra X chromosome, karyotype 47XXY) or Turner’s syndrome (where a female has only one copy of the X chromosome, karyotype 45XO). Both these conditions cause infertility.
Karyotype abnormalities can be total (where every cell in a person’s body has the variation) or mosaic (where only some of the cells in a person’s body has the variation) .
Chromosomal rearrangements are another type of karyotype problem which are much more common in women and men with infertility and are an often a missed issue. This refers to parts of the chromosome that are missing, extra, flipped upside down or in the wrong place. A person can have a “balanced translocation” where they have all the right volumes of the DNA library but arranged in the wrong order. This can cause infertility and recurrent miscarriage in couples where either partner has a balanced translocation.
There are different types of chromosomal translocations, known as Robertsonian translocations or reciprocal translocations. Both cause infertility. Another type of chromosome rearrangement is called an “inversion”. This is where part of a chromosome has been flipped upside down.
It’s not impossible for an individual with a chromosomal rearrangement to conceive naturally and have a child without a chromosomal abnormality, but it is much harder and can sometimes lead to increase in the number of miscarriages.
Who needs the karyotype test ?
Couples who have had recurrent early pregnancy losses.
Couples with secondary infertility (where they have had a child before and are struggling to have another).
Couples with previous failed IVF treatments.
All couples requiring genetic testing of embryos - it is better to perform a karyotype prior to any IVF treatment to ensure we prevent starting a treatment with a high chance of failure.
What can be done during fertility treatment if my karyotype is abnormal?
If it is identified that you or your partner have abnormal karyotype prior to commencing treatment, pre-implantation genetic testing (embryo testing) along with your IVF treatment is indicated. Embryos are grown to the blastocyst stage and are biopsied. Cells of the embryos are genetically tested and only embryos with a normal number and structure of chromosomes will be selected for transfer and implantation.
Cost and turn over ?
The cost of the karyotype blood test is at the pathology clinic's discretion, and the results turn over can be up to 14 weeks. We recommend you undertake the test as soon as possible (usually ordered with other standard bloods) to allow us to review your results prior to starting treatment. Based on the results your treatment may need to be modified to factor in pre-implantation genetic testing. Occasionally and in urgent situation you may wish to proceed without the test results.
We prefer to order this test for your best IVF outcome although this test is not mandatory.