Elective single embryo transfer and cumulative pregnancy rate: five-year experience in a Southern European Country

To compare cumulative pregnancy and live birth rates of single embryo transfer (SET) vs. double embryo transfer (DET) in women <35 years old with good-quality embryos, we designed an observational prospective study carried out between October 2002 and December 2006. Patients who accepted SET were compared with those who decided DET. A total of 628 couples who underwent embryo transfers met the criteria for SET: 52% accepted it, while 47.8% asked for DET. Implantation rate was higher in SET, 46.6% (p < 0.05), whereas pregnancy rate (PR) per transfer was higher in DET, 38.3% (p < 0.05). Twin PR in DET was 26.4% compared with 0.7% in SET (p < 0.05). SET group performed 278 frozen embryo transfer and DET 128. The mean of embryos transferred was the same, resulting in similar pregnancy and twin PR (SET: 24.8% and 21.7% vs. DET: 25.0% and 28.1%). Cumulative PR was 66.2% in SET and 69.7% in DET, not showing significant differences (NS). Likewise, cumulative live birth rates did not show differences. Cumulative twin PR in SET was 7.2% and in DET 26.6%, (p < 0.05). Cumulative PR over time leveled at 15-18 months follow-up in both groups. In Conclusion, in order to reduce twins we support the promotion of SET.