172 ELECTIVE SINGLE EMBRYO TRANSFER (ESET) IN HUMANS DOES NOT AFFECT THE CHANCES OF A SUCCESSFUL PREGNANCY

Abstract

Improvements in human IVF have led to increased pregnancy rates but at the expense of increasing twinning rates. Twins are a bad outcome for the offspring, parents and the healthcare system. An obvious solution to this is to transfer only one embryo and freeze the rest for potential further treatment. This study looked at the effect of doing this on the cumulative live birth rate (when the cryopreserved embryos were thawed and transferred). Patients less than 38 years of age presenting for IVF treatment and with more than two embryos suitable for transfer were offered the chance of transferring only one embryo (elective single embryo transfer, eSET) and freezing the rest. Those patients declining a single embryo transfer had two transferred and served as the controls. Patients not achieving a pregnancy returned for a frozen embryo transfer but were not restricted on the number transferred (to a maximum of two). Cumulative live birth rates were recorded over the ensuing two years. Statistical comparisons were made using paired chi-square tests. The live birth rates from the initial fresh transfer was 41% for eSET (41/111) and significantly higher (53%, P < 0.05) for the two-embryo transfer group. These differences were eliminated when the frozen embryos were factored in, both groups rising to 61% of patients treated (68 and 172 live births, respectively). The twinning rate was significantly reduced (P < 0.01) from 33% in the two-embryo transfer group to 6% (arising from 4 sets of twins in the frozen embryo transfers) in the eSET group. eSET in the fresh embryo transfer cycle does not affect the chances of a live birth and reduces the twinning rate at least fivefold. Currently, 70% of patients under the age of 38 are electing to have eSET.