S-10 Reproductive BioMedicine Online, Vol. 18, Suppl. 3, May 2009 Abstracts – PGDIS: 9th International Symposium on Preimplantation Genetics error from minor somatic mosaicism and from technical probe errors. This method uses a molecular approach with multiple STR markers, which are chosen to lank the translocation breakpoints on both chromosomes involved and which track all meiotic segregations. The STR approach allows for a more rapid test which is not inluenced by low-level mosaicism (suspected to be clinically insigniicant in most cases), is less prone to interpretational error, allows for a greater number of embryos to be analysed and has the potential to differentiate balanced and normal embryos. Materials and methods: Robertsonian and reciprocal translocation carriers, who were having FISH PGD at Sydney IVF, were approached to participate in an evaluation of an alternative PCR-based test method. Embryos assigned as abnormal by FISH-based test results, and therefore not clinically useable, were reanalysed by the alternative PCR- based method. Participating couples provided DNA samples that were used to identify STR markers informative for tracking of chromosome segments. Markers identiied as fully informative were then multiplexed for use. Results: Embryo reanalysis by PCR showed concordant results in 60% of embryos. The remaining embryos assigned as abnormal by FISH showed balanced signal patterns on PCR testing. A closer look at these embryos showed that 80% had inconsistent or conlicting FISH results between cells analysed. FISH error and/or mosaicism appeared likely contributors to these inconsistent results. In every embryo analysed by the PCR testing, the STR peak patterns were easily matched to expected meiotic malsegregation patterns suggesting a high level of test discrimination. 72% of embryos from reciprocal carriers and 26% of embryos from Robertsonian carriers have been shown to be abnormal on PCR analysis so far. These results are consistent with abnormality rates often cited for the sperm or eggs in patients carrying translocations. Conclusion: Increasingly, new techniques for chromosome analysis in embryos are being sought in an attempt to improve on current FISH test method performance. Comprehensive screening techniques such as CGH and micro-array technologies are not, at present, easily integrated into current routine PGD laboratory practices. The method presented here provides a valuable improvement on currently available FISH tests for translocations, especially in test turnaround, test performance and reliability of the information obtained. Results indicate a likely low error rate and provide more reliable chromosome segregation information for each embryo when compared with FISH. Gene location matters: polar body analysis has limited informativity in centromeric genes Altarescu G 1 , Brooks B 2 , Zylber EH 2 , Varshaver I 2 , Eldar-Geva T 2 , Margalioth EJ 2 , Levy-Lahad E 1 , Renbaum P 1 ZOHAR PGD Lab, 1 Medical Genetics Institute; 2 IVF Unit, Shaare Zedek Medical Center, Jerusalem Objective: To assess the degree of heterozygosity and percentage of allele dropout (ADO) of PB1 that are analysed during PGD for monogenic diseases. Introduction: PGD is performed by biopsy of blastomeres or polar bodies utilizing mutation detection and multiple polymorphic marker analysis to minimize misdiagnoses. Because only maternal alleles are analysed in polar bodies, the chances of inding informative markers are higher than in blastomere analysis. An additional advantage is the sequential analysis of PB1 and PB2: when PB1 are heterozygous, this Increased embryo implantation and high birth rates following comprehensive chromosomal screening of in- vitro fertilized embryos Wells D, Fragouli E, Alfarawaty S, Schoolcraft WB, Munné S, Katz-Jaffe M Background: The high frequency of chromosome abnormalities in human oocytes and embryos has a signiicant impact on the success rates of IVF treatment, particularly in patients of advanced maternal age. The preferential transfer to the uterus of euploid embryos may lead to increased pregnancy rate and reduce the risk of spontaneous abortion. However, the screening of embryos for aneuploidy remains controversial, with some recent studies failing to show any improvement in IVF outcome. Materials and methods: Standard strategies for embryo screening involve biopsy of a single cell 3 days after fertilization, followed by analysis of a restricted set of chromosomes. Our study utilized an approach, involving biopsy of several cells on day-5 post-fertilization (blastocyst stage), vitriication of blastocysts, comprehensive chromosome screening using CGH, devitriication and transfer of chromosomally normal embryos. Results: More than 70 patients have now received blastocyst CGH screening. At this point, 15 of the patients have had their embryos devitriied and transferred. The mean maternal age was 37.5 years and most patients had at least one previous failed IVF attempt (mean 1.8). The clinical pregnancy rate (fetal heart detected) per cycle started was 86.7% and a live birth was achieved in 80.0% of cycles, compared with 60% in controls. The probability of an individual transferred embryo implanting and forming a pregnancy was 66.7% compared with 27.9% without screening (P = 0.0003). Conclusions: We describe a robust test for screening the entire chromosome complement of IVF embryos. This method overcomes problems faced by earlier aneuploidy screening techniques and led to improved IVF outcomes. Transfer of euploid embryos resulted in a dramatic increase in embryo implantation rate, indicating that this strategy will greatly beneit efforts to maintain or improve pregnancy rates wile reducing the number of embryos transferred during IVF cycles. The data was also suggestive of an increased live birth rate. The application of a molecular strategy using STR for routine PGD in both reciprocal and Robertsonian translocation carriers Traversa M, Leigh D Sydney IVF, Sydney, NSW, Australia Introduction: Couples who carry translocations can experience subfertility or recurrent miscarriage due to embryo aneuploidy associated with meiosis-based malsegregation of affected chromosomes during spermatogenesis or egg maturation. PGD analysis of structural chromosome abnormalities usually involves testing by FISH on single blastomeres. This technique is known to have limitations, which primarily derive from errors including signal overlap, signal splitting and poor probe hybridization, in addition to embryo mosaicism. As a result, interpretation errors can lead to the loss of suitable embryos or the transfer of unbalanced embryos not detected due to technical error and misdiagnosis. As more laboratories move towards blastocyst biopsy techniques in an attempt to improve on current pregnancy outcomes, other factors such as cell overlap and limited mosaicism start to affect the ability to easily differentiate a true constitutional meiotic chromosomal