Towards a more sustainable balance between optimal live birth rate and supernumerary embryos in ART treatments

To assess the relation between number of inseminated oocytes and cumulative live birth rate (CLBR) in order to provide guidance for limiting the number of surplus blastocysts.

The study was a retrospective, single-center cohort analysis of 1223 ART complete cycles. Cycles were stratified according to female age (≤ 34, 35–38, and 39–42 years) and number of inseminated oocytes (1–5, 6–10, and > 10). Inclusion criteria were indication for IVF/ICSI with own spermatozoa and blastocyst culture up to day 6 of all embryos.

In patients younger than 35 years, insemination of more than ten oocytes produced an increase in overall blastocyst number, CLBR (40.3%, 54.3%, and 75.8%, respectively, for each oocyte group) and surplus embryo rate (12.9%, 27.8%, and 49.7% of cases for each group). Instead, in the middle age group, the use of more than ten oocytes was solely associated with an increase in the rate of surplus embryos (1.25%, 21.33%, and 28.68% of cases after stratification for oocyte number). In older patients, neither CLBR (9.1%, 23.9%, and 24.7%, respectively) nor rate of surplus embryos (2.0%, 7.1%, and 13.4% of cases for each group) were higher in cycles with more than ten inseminated oocytes.

In women up to 38 years, sustainable CLBR are achieved while limiting the number of inseminated oocytes and the resulting blastocysts remaining unused. Based on this notion, novel treatment strategies could pursue high outcome rates, while alleviating the problems derived from surplus stored embryos.