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<ns4:p> <ns4:bold>Background:</ns4:bold> Low (or poor) responder patients are women who require large doses of stimulation medications and produce less than an optimal number of oocytes during IVF cycles. Low responder patients produce few oocytes and embryos, which significantly reduces their chances for success in a preimplantation genetic diagnosis (PGD) cycle. Accumulation of vitrified oocytes or embryos before the actual PGD cycle is a possible strategy that might increase patient’s chances for a healthy pregnancy. </ns4:p> <ns4:p> <ns4:bold>Aim of the study</ns4:bold> : This retrospective study evaluates the efficacy of a PGD program in low responder patients after repeated ovarian stimulation cycles with cumulative vitrification of oocytes and embryos. </ns4:p> <ns4:p> <ns4:bold>Methods:</ns4:bold> Over a period of 30 months, 13 patients entering the PGD program were identified as poor responders after their first ovarian stimulation. These patients started a PGD cycle for one of the following indications: history of recurrent implantation failure (n=1), cystic fibrosis (n=1), X-linked microtubular myopathy (n=1), recurrent miscarriages (n=5), Duchene muscular dystrophy (n=1), chromosomal translocation (n=1) and high sperm aneuploidy (n=1). After multiple ovarian hormonal stimulations patients had either all mature oocytes (Group A; 3 patients) or all of their day 2 embryos vitrified (group B; 10 patients). Mean total number of oocyte collections per patient was 2.3 (range: 2 - 5 cycles). </ns4:p> <ns4:p> <ns4:bold>Results:</ns4:bold> In the actual PGD cycle, all vitrified oocytes from group A patients were warmed and underwent intra cytoplasmic sperm injection (ICSI) followed by culture up to day 3. For group B patients all vitrified day 2 embryos were warmed and cultured overnight. On day 3 of culture, all embryos from Group A and B had blastomere biopsy followed by genetic analysis. In group A, 20 embryos were found suitable for biopsy and genetic analysis; at least one healthy embryo was available for transfer for each patient. For group B, 72 embryos in total were available for biopsy and PGD. All patients, except one, had at least one healthy day 5 embryo for transfer (mean number of 2.1 embryos per transfer). Nine patients had a clinical pregnancy; 7 patients delivered a healthy baby. </ns4:p> <ns4:p> <ns4:bold>Conclusion:</ns4:bold> Low responder patients entering a PGD program might increase their chances for a healthy pregnancy by repeat ovarian stimulation in combination with cumulative oocyte or embryo vitrification. </ns4:p>