A Randomised Control Trial of Three-dimensional Versus Two-dimensional Ultrasound Guided Embryo Transfer in Women Undergoing Artificial Reproductive Technology Treatment

INTRODUCTION

The role and use of 2DUS in gynaecology is undisputed as it forms an integral part of diagnosing pathologies of the uterus, tubes and ovaries. In reproductive medicine, it is of particular significance as it is additionally the most widespread tool available to monitor endometrial thickness, follicular status and growth, allow guided retrieval of oocytes from the ovary and also guided transfer of fertilised embryos into the uterus [1]. These are undoubtedly some of the most critical procedures/steps of ART.

The development of 3DUS has brought somewhat of a breakthrough in the field as now 3D volumes of images can be acquired and analysed live or retrospectively. From a practical perspective, the scanning procedure does not differ from the routine 2D US and the acquisition of a 3D volume requires only a few seconds. Analysis of these volumes allows reconstruction of planes which are not always possible with 2DUS (such as the 3D coronal plane of the uterus). As a result, 3DUS is now considered to be the most accurate non-invasive modality to diagnose uterine anomalies [2, 3]. Furthermore, 3DUS allows accurate volume calculations of structures such as the endometrium and follicles. These new possibilities, coupled with advanced software now also allows for automated measurements of these variables, which may improve accuracy, reduce interobserver variability and increase efficiency of an ART unit [4].

Several publications now in the literature support that 3DUS may play a major role in ART in the future [5-8]. Areas which 3D US may provide additional information are:

• Assessment of ovarian blood flow, follicular volume and growth [9]
• Assessment of endometrial and subendometrial blood flow and volume [10, 11]
• Assessment of precise catheter placement during embryo transfers [12] The latter is perhaps the area which has been the least investigated so far, despite embryo transfer being arguably the step of highest importance throughout the entire ART process. Two preliminary studies have shown that 3DUS guided embryo transfer significantly improves catheter placement compared with 2DUS [13] and can allow for correction of up to 20% of mal-positioned catheters where 2DUS alone has been used [14]. The largest series to date, has demonstrated that by use of 3DUS, the placement of embryos can be performed in the so called maximum implantation potential point, which is where the trajectories of the fallopian tubes meet in the centre of the uterine cavity, where the endometrial thickness and blood flow is thought to be greatest [12]. However, to our knowledge, there has been no randomised controlled trial (RCT) in the literature to systematically test 3DUS versus 2DUS guided embryo transfer with respect to pregnancy outcomes. If 3DUS guided embryo transfer is confirmed to produce a higher pregnancy rate than 2DUS guided embryo transfer, it will have significant impact on the daily clinical practice of ART units worldwide.