Interim Analysis of a Randomized Clinical Trial Comparing Abdominal Versus Transvaginal Ultrasound-guided Embryo Transfer

Aim: Ultrasound-guided embryo transfer appears to improve overall pregnancy outcomes for in vitro fertilization embryo transfer cycles. Most reports are done using a transabdominal ultrasound-guided approach, in contrast to a transvaginal ultrasound, which does not require a full bladder. We sought to determine if either approach was better with respect to clinical pregnancy outcomes.

Methods: This randomized clinical trial took place in a university-based practice with an enrollment of 186 subjects. Secondary measures also included embryo transfer time and degree of cramping and pain, which subjects ranked as none = 1; mild = 2; moderate = 3; or severe = 4.

Results: There were no differences in implantation rates (33.1 + or - 4.1%, + or - standard error vs 31.1 + or - 3.9%, P = 0.78), pregnancy rates (60% vs 54%, P = 0.38), clinical pregnancy rates (48% vs 45%, P = 0.77), and live-birth rates (30% vs 39%, P = 0.37) between transabdominal and transvaginal ultrasound-guided embryo transfer groups. No differences were noted between groups for time required for embryo transfer (157 + or - 279 seconds vs 130 + or - 176 seconds, P = 0.92), uterine cramping (1.2 + or - 0.5 vs 1.2 + or - 0.4, P = 0.4), and the degree of pain (1.4 + or - 0.7 vs 1.3 + or - 0.5, P = 0.13).

Conclusions: Neither transabdominal nor transvaginal ultrasound-guided embryo transfer is more beneficial in optimizing pregnancy outcomes. While delays often occur while waiting for bladder distension for transabdominal ultrasound-guided embryo transfer, uterine position, parity and level of physician comfort should dictate the choice of either approach.