from the embryo) are then removed from the 8-cell embryo for analysis and sent to a certified lab for analysis. The removal of 1 or 2 cells for analysis does not impair either implantation rates or pregnancy rates. Analysis takes up to 2 days to obtain the results. Selection of the embryos to be returned to the body are based on the PGD results.

Over 1000 babies world-wide have been born after PGD. To date there are no reports of increased fetal malformation rates or other identifiable problems due to the process of PGD.

There are errors of analysis associated with the process of PGD. This may be due to various reasons including variations of the chromosomal makeup with individual cells within the embryo (called mosaicism). Errors due to mosaiciscm of the embryo may occur in up to 4% of cases. There may also be a small occurrence of false positives and false negatives in analyses of the cells. It is recommended that patients who undergo PGD still consider amniocentesis during pregnancy to confirm the results.

There are different reasons to consider PGD as part of treatment. Original development of PGD was to reduce the transfer of specific single gene disorders and inheritable gene disorders.

Other common reasons why couples may choose to include PGD as part of their treatment are the following:

• To reduce using abnormal embryos that can result when the eggs are from a patient of advanced maternal age (> age 37) (called preimplantation genetic screening).

• Couples who have been experiencing recurrent miscarriage where it may suspected that abnormal embryos are leading to this problem period.

• Couples who have been experiencing recurrent implantation failure during IVF for unknown reasons.

It is not clear in these last indications if PGD is truly beneficial as research studies have given conflicting results.