A prospective randomized controlled trial of 3D versus 2D ultrasound-guided embryo transfer in women undergoing ART treatment.

Study Question: Does three-dimensional (3D) versus two-dimensional (2D) ultrasound (US) guidance during embryo transfer (ET) increase the ongoing pregnancy rate in women undergoing ART treatment.

Summary Answer: There is no significant difference in the ongoing pregnancy rate of women undergoing 3D versus 2D US-guided ET.

What Is Known Already: Studies have suggested that 3D US may confer additional benefits compared with 2D US during ET, although this has not been tested within the context of an RCT.

Study Design, Size, Duration: This was a single-blind, single centre prospective RCT performed between April 2015 and April 2016. A total of 481 recruited women were randomised into either a 3D or 2D US-guided ET group.

Participants/materials, Setting, Method: Women younger than 42 years in whom the endometrial cavity could be adequately visualised by US underwent ET in a university ART unit following a standard treatment protocol. All US examinations were performed by a single operator. In both 3D and 2D US groups, the inner catheter tip was aimed at the centre of the uterine cavity. The primary outcome measure was ongoing pregnancy rate, defined as the presence of at least one foetus with heart pulsation at 8 weeks of gestation.

Main Results And The Role Of Chance: There was no significant difference in the ongoing pregnancy rate between the 3D and 2D US groups (35.4% versus 37.1%, P = 0.70; rate ratio 0.96, 95% confidence interval 0.75-1.21). There were also no significant differences in terms of positive hCG rate, biochemical pregnancy rate, implantation rate, clinical pregnancy rate, miscarriage rate, ectopic pregnancy rate and multiple pregnancy rate.

Limitations, Reasons For Caution: This study recruited unselected women undergoing routine ET and was therefore not sufficiently powered to assess differences in subsets of women.

Wider Implications Of The Findings: Although 3D US may be a modern method for demonstrating the ET procedure, it should not be currently recommended as a strategy to improve clinical outcomes in women undergoing ART treatment.

Study Funding/competing Interests: This study was funded by the Health and Medical Research Fund of Hong Kong. The authors have no conflicts of interest to disclose.

Trial Registration Number: ClinicalTrials.gov Identifier: NCT02413697.

Trial Registration Date: 4 April 2015.

Date Of First Patient's Enrolment: 20 April 2015.