The Effect of Uterine Length Measurement before Embryo Transfer versus Transabdominal Ultrasound-Guided Embryo Transfer on FET Cycle Outcome: A Randomised Clinical Trial.

Background: Embryo transfer (ET) is an important step in assisted reproductive technology. Uterine length measurement before ET (ULMbET) enables the determination of catheter length and anatomical variation before the ET. Therefore, in this study, we aim to compare ULMbET and transabdominal ultrasound-guided ET (TAUGET).

Materials and methods: This open-label randomised clinical trial enrolled 264 women who were scheduled for frozen- thawed ET (FET) cycles. The women were randomised to the ULMbET or TAUGET group for ET. The primary outcome of this study was clinical pregnancy.

Results: A total of 132 women were randomly assigned to the ULMbET group and 132 women to the TAUGET group. However, four women in the ULMbET group did not receive the allocated method after randomisation. Finally, 128 women from the ULMbET group and 132 women from the TAUGET group were assessed. No statistically significant differences existed in chemical pregnancy rate (31.3 vs. 36.4%, P=0.384), clinical pregnancy rate (23.4 vs. 28%, P=0.397), and implantation rate (15 vs. 17.8%, P=0.401) between the ULMbET and TAUGET groups, respectively.

Conclusion: The results of this clinical trial show no differences in pregnancy outcomes in FET cycles following ULMbET and TAUGET (registration number: IRCT20110509006420N240).