The world’s  experience over  more than 20,000 cycles of PGD shows that the procedure is quite efficient, with a diagnostic accuracy of over 90% or even higher in some genetic studies. The error rate of 10% includes both false positive and false negative results.

Embryo transfer is not always a guarantee when a PGD procedure is performed, because all embryos might turn out to be genetically abnormal, or not embryogenic or unviable. Therefore, it is important to predict the possibility of finding normal embryos in accordance with the genetic disorder and ovarian reserve before starting the PGD. In general, this type of diagnosis requires a normal response to ovarian stimulation and the eggs must be embryogenic. For recessive disorders 3 out of every 4 embryos are potentially transferable, while for dominant disorder 1 out of every 2. For reciprocal translocations 1 out of every 5, for Robertsonian translocation 1 out of every 4, and for HLA typing 1 out of every 4, etc.

There are several potential problems that could occur with the FISH technique, as follows: hybridization problems, misinterpretation of the fluorescent signals, the inability to detect structural abnormalities, and the possibility that the same embryo has cells with different chromosome numbers. Therefore, the status of one cell cannot always be extrapolated to the entire embryo.  Problems with PCR studies may be due to complications during DNA amplification, potential contamination with exogenous DNA and other technical difficulties.

These difficulties may lead to misdiagnosis that could prevent from transferring a normal embryo or could lead to an abnormal embryo transfer. Due to this possibility of misdiagnosis and the possibility of genetic mosaicism, the implementation of prenatal diagnosis CVS or amniocentesis to confirm the results of PGD is recommended.