For people who have a chance of passing on an inheritable genetic disorder to their child, such as Cystic Fibrosis, Huntington’s, Beta-thalassemia, Fragile X and Spinal Muscular Atrophy (SMA). These are caused by a change or mutation in the gene.
PGT-M or Preimplantation Genetic Testing - Monogenic disorder can be performed to select and transfer embryos free of the genetic condition. PGT-M is beneficial for:
- women who have had previous pregnancy termination(s) due to a serious genetic disorder
- couples who already have a child with a genetic disorder
- couples who have a family history of any inherited genetic condition
Useful to know:
PGT-M cannot be used for gender selection in Malaysia.
PGT-M can also screen for aneuploidy at low resolution.
FAQ about Karyomapping
How does karyomapping differ from other PGT-M tests?
Until recently, PGT-M tests for disorders caused by inheritance of a defective gene had to be tailor-made for each couple. This required weeks or months of work by highly skilled scientists, meaning that costs were high and there was often a long wait before IVF treatment could begin. By contrast, karyomapping provides a test for PGT-M of almost any known gene defect with a rapid turnaround time. The accuracy of Karyomapping is improved as there are approximately 300,000 markers throughout the whole genome to determine the inheritance of the gene.
Who is karyomapping for?
You may know that you are a carrier of a genetic disorder because you already have an affected child, or you may be aware of a family history of the disorder and have had your DNA tested.
Karyomapping is a new technique that allows couples, known to be carriers or affected with an inherited condition, to avoid passing on that disorder to their offspring. The technique works by screening embryos for the disorder before implantation in the womb (uterus)—a technique called Preimplantation Genetic Testing - Monogenic disorder, or PGT-M.
Using PGT-M greatly reduces the chance that a fetus will be affected by the genetic disorder and, consequently, it is much less likely that termination of a pregnancy will need to be considered, or that an affected child will be born.
Why is IVF required?
In order to carry out PGT-M in vitro fertilization (IVF) is essential. This process involves collecting several eggs from the ovaries and fertilizing them outside the body (in vitro) to produce several embryos. Each of the embryos can then be tested to find out which are suitable for transfer.
Only the embryos that are predicted to be free of the genetic condition are transferred to the uterus and, consequently, any pregnancy that begins has a low risk of being affected by the disorder.
How does Karyomapping work?
A blood sample is taken from the father, the mother, and a close relative of known disease status (affected,unaffected or a carrier). In most cases, the relative tested is a child of the couple. This relative is referred to as ‘the reference’.Karyomapping looks at the chromosomes, the long rod-like structures that are found in cells and contain the genes.
Karyomapping examines the chromosomes of the mother, father, and the reference at approximately 300,000 different points and finds a DNA fingerprint unique to the chromosome that carries the defective gene. It is then possible to test embryos produced using IVF for this fingerprint revealing those that have inherited the affected chromosome.
If the fingerprint characteristic of the chromosome carrying the defective gene is not detected, then it can be inferred that the embryo has inherited normal copies of the gene and is therefore likely to be free of the disorder. Embryos of this type are good candidates for transfer to the mother’s uterus (womb).
Thalassaemia is an inherited blood disorder where due to the instability of the wall of the red blood cell (RBC), the patient constantly suffers from anaemia (low levels of haemoglobin, the oxygen carrying part of the RBCs).
- It is estimated that one in 20 Malaysians are thalassaemia carriers, which is about 1.5 million Malaysians, affecting mainly the Chinese.
- If both parents of a child are thalassaemia carriers, there is a 25% chance the child have major thalassaemia, which is a serious condition.
- PGT-M now offers a chance for the couple to have a disease free child by testing the embryos created from IVF for the thalassaemia gene before being implanted into the womb.
- This also effectively stops the thalasaemia gene from being passed down to the subsequent generations.