Objective: To verify that the number of retrieved oocytes influence the following morphological quality of transferred embryos and the success of IVF treatment. Design: A retrospective study. Setting: Clinic of assisted medicine and gynecology, Zlin. Methods: By observing the collection is composed of 837 IVF cycles with embryotransfer, which were practised between June 2002 and December 2004. To observe the number of retrieved oocytes, following morfological quality of transferred embryos, (number of clinical pregnancies). Results: We found that in cycles with more retrieved oocytes (7 oocytes and more), there were embryos of first morphological quality transferred significantly more frequently (59.2% cycles, p<0.001) than in cycles with 1–6 retrieved oocytes. Morphologicaly abnormal embryos were found in cycles with more retrieved oocytes (7 oocytes and more) and transferred significantly less frequently (13.1% cycles, p<0.001) than in cycles with 1–6 retrieved oocytes (34.8% cycles). We have found that on the retrieval of 16–18 oocytes, there were embryos of first morphological quality transferred in 67.4% cycles of treatment (p=0.002). The number of cycles with transferred morphological abnormal embryos is decreasing in relation with increase of oocyte retrieval (p=0.002). Most of clinical pregnancies were achieved in IVF cycles with retrieval of 16–18 oocytes (clinical pregnancies was achieved in 50.0% cycles, p<0.001). Conclusion: The results show that the number of retrieved oocytes was influenced following morphological quality of transferred embryos. In IVF cycles with more retrieved oocytes there are transferred embryos of first morphological quality more frequently. These embryos have higher implantation potential. The number and quality retrieved oocytes are possibly more effective with type and dosing of hormonal stimulation, which should be suitable for every patient.

        Key words: number of retrieved oocytes, morphological quality of embryos, clinical pregnancy