The position of the euploid blastocyst in the uterine cavity influences implantation

Abstract Research question Does the position of the euploid blastocyst in the uterine cavity upon transfer, measured as distance in millimetres (mm) from the fundus (DFF) to the air bubble, influence implantation potential? Design A total of 507 single/double euploid frozen embryo transfer (FET) cycles at blastocyst stage were included retrospectively between March 2017 and November 2018 in a single center. The patients were on average 33.3 years old. The FETs were performed in natural cycles (NC; n=151) or hormone replacement therapy cycles (HRT; n=356). Results Of the 507 transfers, 370 (73%) resulted in a pregnancy, defined as hCG > 15 IU and 302 (59.6%) in a clinical pregnancy leading to an implantation rate of 61.5%. When comparing the number of embryos transferred and the quality of the blastocysts, the pregnancy rate, clinical pregnancy rate and implantation potential were significantly higher after double embryo transfer (DET) (p Conclusions The depth of blastocyst replacement inside the uterine cavity may influence the pregnancy and implantation rates and should be considered as an important factor to improve the success of IVF cycles.