Aneuploidy is a genetic abnormality involving too many or too few chromosomes than the normal 23 pairs. Aneuploidy is the cause of conditions including Down syndrome, Patau syndrome, and Edward syndrome.

PGT-A is particularly useful if you:

• Have experienced repeatedly unsuccessful embryo transfers
• Have had a previous pregnancy affected by aneuploidy
• Are a mother-to-be older than 35 years
• Have experienced recurrent miscarriage

Some medical conditions are caused by a single abnormal gene. Examples of these include Huntington disease, thalassaemia, and cystic fibrosis. PGT-M is a genetic test that covers over 350 single-gene diseases, both common and rare.

You may be recommended PGT-M if you:

• Have a personal or family history of a confirmed genetic condition with the potential to pass it on to your future children
• Or your partner are healthy but are known carriers of a single-gene condition that may be expressed in your future children, such as spinal muscular atrophy

Sometimes, a cell may have the correct number of chromosomes but in a different arrangement. This is known as balanced translocation or chromosomal inversion. You may not be affected by any health issues due to this as you still have the correct number of chromosomes, but there is an increased risk of passing on an unbalanced amount of chromosome information in your eggs or sperm.

If you or your partner are known to have a chromosomal inversion, Dr Kate will recommend you consider PGT-SR.