Background: The general trend in PGD is the analysis of higher numbers of chromosomes requiring up to 2 rehybridizations. However, there may be diminishing returns as the increase in the number of chromosomes analyzed will result in a minimal increase in sensitivity and a greater decrease in specificity (may yield a higher number of indeterminate or false-positive abnormal embryos).

Objective: The purpose of this study was to evaluate the percent of embryos found to be normal out of total number of embryos biopsied in IVF cycles employing PGD using a 5 chromosome panel vs. a 9 chromosome panel and the effect on pregnancy rates.

Materials and Methods: This was a retrospective analysis of 226 patients undergoing IVF with PGD from September 2003 to May 2004. The medical records were reviewed for age, number of embryos biopsied, number of normal embryos per PGD, number of embryos transferred, and pregnancy outcome for 4 physicians with similar stimulation protocols. 55 patients had necessary information documented and were used for the study. Student t-test for two samples and chi-square test were used for statistical analyses.

Results: The data for the two groups is shown in Table 1. The mean age, number of total embryos biopsied and number of embryos transferred were similar between the two groups. The 5 chromosome groups had higher number and percent of normal embryos as diagnosed by PGD (p<0.005, p<0.0001). The pregnancy rate was higher in the 5 chromosome group, but this did not reach significance. The patients able to conceive (5 or 9 chromosome panel) had a significantly higher number of normal embryos as diagnosed by PGD (4.0 ± 2.2 vs. 2.0 ± 0.97, p<0.0005) and a higher number of embryos transferred (2.5 ± 0.7 vs. 1.9 ± 0.7, p<0.005) as compared to those unable to conceive.

Means	5 Chr PGD	9/10 Chr PGD
Age	36	37
# Embryos biopsied	7.36	6.73
# Normal embryos	4.0	2.4
%Normal embryos	61	38
# Embryos transferred	2.32	2.15
Pregnancy rate	68%	50%

Conclusions: A trend towards higher pregnancy rates was noted in the 5 chromosome PGD group. This may indicate that with increased number of chromosomes analyzed there is a greater decrease in specificity with a higher number of false-positive abnormal embryos, resulting in fewer embryos available for transfer. Therefore, PGD using a 9 chromosome panel offers little added value over the 5 chromosome panel with a potential adverse effect on pregnancy rates.