Embryos cultured in vitro with multinucleated blastomeres have poor implantation potential in human in-vitro fertilization and intracytoplasmic sperm injection.

The aim of the present study was to investigate pregnancy rates ensuing from transfer of embryos with multinucleated blastomeres. In our in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) programme, 1735 embryo transfers were performed from January 1, 1995 to August 31, 1996. In 136 of these transfers at least one embryo with one or more multinucleated blastomeres was present per transfer (study group). For each of these 136 transfers, two matched controls with transfer of exclusively mononucleated embryos were selected (control group). Matching was carried out according to age, method of fertilization (IVF or ICSI), number of transferred embryos and quality score of transferred embryos. In the study group, there were eight transfers of exclusively multinucleated embryos from which one pregnancy ensued and 128 transfers in which multinucleated and mononucleated embryos were transferred together leading to 23 pregnancies. The overall clinical pregnancy rate per transfer was 16.9% in the study group versus 28.7% in the control group (P = 0.01). The ongoing pregnancy rate per transfer was 13.2% in the study group versus 23.2% in the control group (P = 0.03). The implantation rate per transferred embryo was 6.0% in the study group versus 11.3% in the control group (P = 0.003). This study shows that embryos with one or more multinucleated blastomeres have a poorer implantation potential than embryos with mononucleated blastomeres. Transfer of embryos with multinucleated blastomeres should hence only be considered when insufficient numbers of embryos with only mononucleated blastomeres are present.