Predictive value of the cumulated embryo score on the incidence of multiple pregnancies in IVF cycles.

Aim: In order to reduce the risk of multiple pregnancies after IVF-ET, either a limitation to two of the number of transferred embryos, the transfer of a single blastocyst after coculture on feeder cells or the use of an embryo scoring system (1) have been proposed. The advantage of the cumulated embryo score (CES) is to take into account in a single value the number of embryos, the number of blatomeres and the morphological grade. The purpose of this study was to determine a threshold value for the CES, useful in routine laboratory and clinical conditions, in order to properly advise the patients prior to transfer on the risks of multiple pregnancies and to propose a limitation to two transferred embryos when this risk is known to be high. Material and methods: The transfer cycles of fresh and frozen-thawed embryos, cryopreserved at the 2 pronucleate stage, performed during 1993 to 1995 were analyzed. Cycles in which assisted hatching was performed were excluded. Embryos were graded from I to IV just prior to embryo transfer (ET) depending on the respective sizes of the blastomeres and proportion of anucleated fragments. The maximum number of transferred embryos was limited to three. Clinical pregnancies (CP) were defined by the presence of a foetal heart activity 28-35 days after transfer. Results: Distribution of the single and multiple pregnancies according to the CES for fresh embryos is shown on the following table. CES ET Clinical pregnancies CP/ET (%) Single (%) Twin (%) Triplet (%) 0-9 91 6 6.6 6 0 0 10-19 177 37 20.9 28 8 1 20-29 191 54 28.3 46 8 0 30-39 186 56 30.1 27 19 10 ≥40 143 53 37.1 34 14 5 Total (%) 788 206 26.1 141 (68%) 49 (24%) 16 (8%) Above a CES of 30, 33/109 (30%) gave rise to twin and 15/109 (14%) to triplet pregnancies. In case of frozen-thawed embryos, a similar trend was observed with 3/14 (21%) twin and 2/14 (14%) triplet pregnancies. Conclusion: Both the clinical and the multiple pregnancies depend on the CES at the time of transfer. Above a CES of 30, we propose to limit to two the number of transferred embryos. This choice, which is discussed with the patient, has a direct incidence on our freezing policy and will affect the final discussions on the Swiss Law. (1) Steer et al., Hum. Rep. 7, 117-119 (1992