Chromosome translocations and other structural abnormalities

Can PGD help if you or your partner carries a structural chromosome rearrangement?

Yes. PGD for structural chromosome rearrangements allows couples to decrease the risks of miscarriage and can increase the chance of a healthy baby. Regardless of whether it is a man or woman carrying a structural chromosome rearrangement, the risk is increased for a pregnancy with an unbalanced chromosome complement, which can cause birth defects, mental retardation, and/or miscarriage.

What are Structural Chromosome Rearrangements?

The genetic material in our bodies is packaged in units called chromosomes. Occasionally, pieces of different chromosomes break off and switch positions. At least one in 800 healthy individuals carries a balanced structural chromosome rearrangement.

Are all structural chromosome rearrangements identical?

No. Both men and women can carry either a reciprocal translocation, Robertsonian translocation or an inversion. In a reciprocal translocation, the ends of any two chromosomes break off, exchange and reattach. A Robertsonian translocation involves the joining of any two of the following chromosomes: 13, 14, 15, 21 or 22. Individuals with a Robertsonian translocation have 45 chromosomes, instead of the normal 46, because the two chromosomes stuck together are counted as one. In an inversion, a segment within any chromosome becomes detached, flips around and reattaches at the same position.

Why is a balanced chromosome rearrangement a problem if you wish to have children?

Many individuals with apparently balanced structural rearrangements are healthy, as they have a complete set of genetic information except that it has become reorganized. Problems can occur as these rearranged chromosomes pair up to divide to form egg or sperm cells because they often line up improperly. Egg or sperm cells may end up with missing or additional chromosomes. For this reason, couples may experience repeated miscarriages or may have a child with birth defects and/or mental retardation. The likelihood of failure to conceive, miscarriage or the birth of a child with abnormalities varies greatly according to the extent of the rearrangement and the specific chromosomes involved.

Read our team's articles on PGD for chromosomal translocations