Genetic problems within the embryo
One of the most common reasons why IVF is unsuccessful, or why miscarriages occur, is because of chromosomal abnormalities in the embryo.
Up to 70% of embryos, whether created naturally or through IVF, are lost before birth. This usually occurs within the first three months of pregnancy, most often before implantation.
What is a chromosome?
A human cell contains genetic material arranged in dense strands, called chromosomes. A normal cell will contain 23 pairs of chromosomes. Fertilisation combines 22 chromosomes and an X chromosome from the mother’s egg with 22 chromosomes and either an X or Y chromosome from the father’s sperm. An embryo then has 46 chromosomes – if it’s a female, with two X chromosomes, and if it’s a male, with an X and a Y chromosome.
If the cells of an embryo contain the wrong number of chromosomes this is called aneuploidy, and causes the embryo to develop abnormally. Women over 38 years of age are at greatest risk of conceiving a baby with a chromosomal abnormality.
Sometimes pieces of chromosomes break off and attach to the ends of other chromosomes. You would then have a normal number of chromosomes (known as balanced translocation), but your children may inherit the chromosome with one part missing, or the chromosome with an extra part (unbalanced translocation). Embryos with unbalanced translocations will usually miscarry or fail to implant.
Dr Leeanda Wilton leads our Preimplantation Genetic Diagnosis (PGD) team. She found that testing for only 8 to 9 chromosomes in an embryo is inadequate, as up to 30% of embryos thought to be normal had an error (chromosome abnormality) on another chromosome that they were not able to test. Our pioneering research in this field has resulted in a new approach to testing for chromosomal abnormalities, Advanced Embryo Selection.
Testing for genetic diseases
A gene is a sequence of DNA (genetic material) on a chromosome with a particular function. Humans have up to 20,000 different genes. When the DNA sequence on a particular gene is altered, a genetic abnormality such as cystic fibrosis or thalassaemia may result. It is now possible to test embryos for many single gene disorders or chromosomal abnormalities with Preimplantation Genetic Diagnosis (PGD).
Some of the most common conditions tested for include:
• Huntington's disease (direct and exclusion)
• Cystic Fibrosis
• Duchenne muscular dystrophy
• BRCA1/BRCA2 (hereditary breast / ovarian cancer)
To find out more about genetic testing, please phone 1800 111 483 or Contact us online...
Find out more about Advanced Embryo Selection for chromosomal abnormalities...
Find out more about Karyomapping for single gene disorders...