What are the indications for PGD ?
PGD can be used for diagnosis of single-gene defects or chromosomal abnormalities. Single-gene defects are classified into two categories: autosomal recessive and autosomal dominant. Autosomal recessive disorders (i.e. cystic fibrosis, -thalasemia, Tay-Sachs disease, sickle cell anemia, etc) require both partners to be carriers of the abnormal gene. These couples have a 25% risk of having a child affected by the disease. For autosomal dominant disorders (like myotonic dystrophy, Huntington’s disease, etc) individuals carrying a single defective gene are affected. Chromosomal aberrations that can be diagnosed by PGD include abnormal number of chromosomes (aneuploidy) and specific rearrangements of the chromosomes (translocations). While most embryos with abnormal chromosomes don’t survive, fetuses carrying an extra chromosome 13, 18 and 21 (Down syndrome) can survive to term. There is extensive evidence that the higher infertility rates in older women are due to an increase in embryos w
