Objective: The aim of this retrospective study was to assess the influence of the number of transferred embryos on multiple pregnancy. Design: Retrospective clinical study. Setting: Department of Obstetric and Gynecology FN UP, Olomouc. Methods: Over the last seven years 572 embryotransfers (ET) have been performed in our centre. Results: Of the 173 pregnancies (P) achieved there were 56% singletons, 35% twins and 9% triplets. One embryo was transferred in 10% of cases and all 8 pregnancies (15% P/ET) ended with a live birth. Two embryos were transferred in 17% of cases. The pregnancy rate was 20% P/ET, 55% of pregnancies were twins and 10% pregnancies were lost in abortion or ectopic pregnancy. Three embryos were transferred in most cases (62%). The pregnancy rate was the highest in this group (36% P/ET) with 13% twins and 3% triplets. The overall pregnancy loss was 16%, the highest loss, 27%, recorded in triplets. Four embryos were transferred in 11% of cases. The pregnancy rate decreased to 28% P/ET, as well as the number of twins (6%), while the number of triplets increased slightly (5%). Pregnancy loss occurred only in singleton pregnancies. Conclusion: We can conclude that in our setting the pregnancy rate increases with a higher number of embryos up to three embryos transferred. Unfortunately, the higher pregnancy rate with three embryos transferred is on the expense of a higher risk and losses due to multiple pregnancy. Therefore we recommed to transfer two embryos unless there are some specific rea- sons.

        Key words: IVF and ET, number of transferred embryos, multiple pregnancy