A formal comparison of the practice of assisted reproductive technologies between Europe and the USA.

In this study, we compared pregnancy and delivery outcomes after the utilization of assisted reproductive technologies (ART) in Europe and the United States (US). ART outcomes were compared between Europe and the US for the year 2001, based on formal reports published by the European Society for Human Reproduction and Embryology (ESHRE) and the Center for Disease Control and Prevention (CDC) in collaboration with the American Society for Reproductive Medicine (ASRM) and Society for ART (SART). Europe utilizes ART at approximately twice the rate of the US (P < 0.001). United States patients showed a significantly decreased likelihood of reaching oocyte retrieval (P < 0.001) and embryo transfer (P < 0.001). Despite this lower chance of reaching oocyte retrievals and embryo transfers, US patients experienced significantly higher clinical pregnancy rates (P < 0.001) and delivery rates per started cycle (P < 0.001) than European patients. Amongst patients reaching oocyte retrieval, the difference in clinical pregnancy rates and live birth rates was even more pronounced in favour of the US. However, US patients received significantly more embryos per embryo transfer (P < 0.001) and experienced a significantly higher multiple pregnancy rate (P < 0.001). Significant differences in favour of US patients in pregnancy rates and live birth rates were also observed for frozen embryo cycles and oocyte donation cycles, where the difference was most pronounced. The better pregnancy and live birth outcomes in the US are not explainable by the transfer of larger embryo numbers alone.