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Why Do Couples With Infertility Need To Have A Karyotype Done?

Posted on November 13, 2019


Karyotype testing for men and women suffering infertility can provide extremely useful information that helps your doctor to get to the bottom of your problem. Karyotypes can diagnose chromosomal abnormalities, a cause of infertility that is relatively common and underappreciated. Where a karyotype is normal, a certain set of problems are ruled out, allowing us to focus on what is really going on.

Where a karyotype is the problem, doing the test is the only way to find the answer. While an abnormal karyotypes can cause physical sperm problems, many men with Karyotype issues such as balanced translocations have normal looking sperm that carry DNA problems that cause infertility and miscarriages for them and their partner.

It’s important also for doctors considering DNA testing of embryos through IVF and karyomapping to know a couple’s karyotype results.

What does a karyotype show?

To understand what a karyotype shows, we need to explain a bit about cells and DNA.

What is a cell?

Our bodies are made up of cells. They are little units that make up all our tissues and organs, from our brains, skin, heart and lungs to our ovaries and  testes. Eggs (oocytes) and sperm are cells.

Most cells in our bodies have a whole edition of the DNA library that makes us who we are. Eggs and sperm are special. They each give only half the amount of DNA that makes us who we are. This is a way that we inherit our DNA library from both our genetic parents.

Cells keep their DNA in a place called the nucleus. Here the DNA is arranged in volumes called chromosomes. Each chromosome is made up of hundreds or thousands of genes (they can be different sized). If chromosomes are the volumes of the DNA library, genes are the pages. Genes code for all kinds of proteins that determine our physical traits.  In different cells of our bodies, different genes are switched on and off, determining the cell’s individual function. However, each cell has a whole copy of a person’s DNA library and this is extremely important. This is necessary for cells to function normally and in the case of sperm and eggs, to make healthy human babies.

What is the normal number of chromosomes?

Humans are supposed to have 46 chromosomes, 23 from each parent, arranged in pairs. There are 22 chromosomes known as autosomes and apair of sex chromosomes, either XX (female) or XY (male).

When the autosomes (chromosomes 1 to 22) were discovered and numbered, they were allocated a number in order of their size, which varies. Number 1 is the biggest autosome and number 22 is the smallest. The X chromosome is much bigger than the Y chromosome, which is one of the smallest chromosomes.

Types of karyotype problems:

Karyotypes can be abnormal in many ways. Some people have the wrong number of chromosomes which can present as a genetic syndrome. Examples are 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 of these conditions cause infertility.

Karyotype abnormalities can by total (where every cell in a person’s body have the problem) or mosaic (where only some of the cells in a person’s body have the problem) .

Chromosomal rearrangements are another type of karyotype problem which are much more common in women and men with infertility and are an often missed issue. This refers to where parts of the chromosome 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 arranged in the wrong order. When this person mixes up their DNA making egg or sperm, instead of exactly half the DNA being passed on, the egg and sperm can become “unbalanced”. Unbalanced eggs, sperm and embryos cannot make normal babies. This is the basis of infertility and frequent miscarriages in couples where either partner has a balanced translocation.

There are different types of chromosomal translocations, known as Robertsonian traslocations or reciprocal translocations.  Both cause infertility. Another type of chromosome rearrangement is called an “inversion”. This is were part of a chromosome has been flipped upside down.

It’s not impossible for a couple where a man or woman has a chromosomal rearrangement to have normal babies naturally, but it is much much harder. In addition, some unbalanced chromosomal arrangements passed on to babies by a man or a woman with a balanced chromosomal rearrangement themselves, can cause serious birth defects.

Who needs a karyotype performed?

Karyotype problems have often been missed in couples who have had recurrent early pregnancy losses that are not detected clinically and present like “delay to conception”. Karyotype problems are also often missed in couples who have secondary infertility (where they have had a child before and are struggling to have another).

Karyotype problems can be the cause of previous failed IVF treatments. The only way to diagnose the problem is to do the test. All couples who have unexplained or partially explained primary or secondary infertility of > 12 months duration should routinely have a karyotype performed as part of their infertility work up.

All couples requiring genetic testing of embryos also need to have a karyotype performed. 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.

Any type of karyotype abnormality causes a couple to have increased risk of infertility and birth defects.

What can be done to help me conceive if I have an abnormal karyotype?

If a couple have an abnormal karyotype which explains their fertility problems, we often turn to IVF and use preconception genetic testing of embryos. In the case of chromosomal rearrangements, this is known as PGT-R.

Embryos are grown to the blastocyst stage and are biopsied. Cells of the embryos are genetically tested and only chromosomally balanced embryos are transferred. This technique is highly successful for infertile couples with this problem.

How long does the karyotype test take?

Karyotypes are performed from cultured white blood cells extracted from a blood test. The process of growing cells to an advanced cell division stage and analysing them takes approximately two weeks.

In addition, if your karyotype has been outsourced to a specialised laboratory by the pathology collector where your blood was taken, results may take longer to return (up to a month).

Where to now?…

If you’re struggling to conceive and would really love to have another baby, we’re here to help. Reach out by making an appointment as a couple for a thorough fertility health check at Women’s Health Melbourne.

 


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