What is the most relevant standard of success in assisted reproduction?: The value of cryopreservation on cumulative pregnancy rates per single oocyte retrieval should not be forgotten.

The most relevant standard of success in IVF has been discussed widely. An optimal standard should reflect both the risk aspects and the effectiveness of the treatment. The most important parameter for the couple is the ultimate cumulative delivery rate per started cycle. Even if the long-term follow-up of the treatment cycles is difficult in practice, we would stress that more emphasis should be given to embryo freezing, in order to maximize the efficiency of the IVF/ICSI cycles. The contribution of embryo cryopreservation in elective single embryo transfer cycle programmes may result in a cumulative delivery rate of >50%. In Finland, the implementation of single embryo transfer has been possible with good cryopreservation programmes. The effect of this strategy has been seen in a decrease in the proportion of twin deliveries after assisted reproduction, being 13.9% for 2002, as well as a reduction of the proportion of multiple births in the nationwide Medical Birth Registry.