Attempts to increase the probability of a successful pregnancy in in-vitro fertilization (IVF) treatment by increasing the number of embryos transferred automatically also increase the probability of multiple pregnancies and their attendant risks. Even where the number of transferred embryos is limited to a maximum of three as in this and other centres, there is a high incidence of twins and triplets. The question therefore arises whether the number of transferred embryos should be further limited to a maximum of two in cases where the prognosis is otherwise good. The only objection to this idea is a possible lowering of pregnancy rate. The present study set out to investigate this question. No significant lowering of pregnancy rate was found, so that limiting the number of transferred embryos to two where the prognosis is otherwise good has now become standard practice in our centre. A good IVF prognosis was defined by the following criteria: first attempt for IVF, less than 37 years old, and good embryo development. From 183 patients fulfilling these criteria, 80 agreed to the transfer of two embryos (group 1) and 103 opted for a triple transfer (group 2). Patient characteristics and embryology results were similar in the two groups. In group 1, 34 patients (42.5%) became pregnant and in group 2, 50 (48.5%). This difference is not significant. Similarly, twin pregnancy rates in both groups were high; eight twin pregnancies (23.5%) in group 1 and 12 (24%) in group 2. For the triplet pregnancy rate of 18% (nine triplet pregnancies) in group 2, there was obviously no parallel in group 1. After thawing about half of the cryopreserved embryos and subsequently replacing them, preliminary cumulative pregnancy rates of 52.5% in group 1 and 53.4% in group 2 were obtained. Future results from cryopreservation should provide relatively better outcomes for group 1 since all the patients in this group had at least one embryo frozen and fewer embryos replaced in the fresh cycle.
