Is Pre-implantation Genetic Diagnosis effective?

Success with PGD depends upon what it is being used for. PGD is effective in the following situations:

Where one half of a couple knows that he/she is carrying a gene which can put their baby at a high risk of a genetic disease. Genes are passed down from the parents to the baby and these include ‘faulty’ genes. If screening shows that the embryo has inherited this gene then the couple have the choice of terminating the embryo.
This means that they get a healthy embryo without this faulty gene.
If one half of a couple is a carrier of a ‘chromosomal translocation’. This means that he/she has genes in which the chromosomes are disordered to the extent that parts of chromosomes have broken off and attached themselves to other chromosomes.
The big risk here is that of birth defects and miscarriages.

This screening will test all embryos for chromosomal abnormalities. Only normal embryos will be implanted into the uterus.

For aneuploidy screening: all embryos are screened prior to implantation because the woman is over 38 or the couple have experienced several failed IVF cycles.
Doing this does not increase the chance of pregnancy but it is useful if a couple know that they are at high risk of passing on a defective gene.