Evidence and consensus on technical aspects of embryo transfer

Abstract

Background: Ultrasound-guided embryo transfer (US-GET) is a widely performed procedure, but standards for the best practice are not available.

Objective and rationale: This document aims to provide an overview of technical aspects of US-GET after considering the published data and including the preparation for the embryo transfer (ET) procedure, the actual procedure, the post-procedure care, associated pathologies, complications and risks, quality assurance and practitioners' performance.

Search methods: A literature search for evidence on key aspects of the ET procedure was carried out from database inception to November 2021. Selected papers (n = 359) relevant to the topic were analysed by the authors. The following key points were considered in the papers: whether ultrasound (US) practice standards were explained, to what extent the ET technique was described and whether complications or incidents and how to prevent such events were reported. In the end, 89 papers could be used to support the recommendations in this document, which focused on transabdominal US-GET.

Outcomes: The relevant papers found in the literature search were included in the current document and described according to the topic in three main sections: requirements and preparations prior to ET, the ET procedure and training and competence for ET. Recommendations are provided on preparations prior to ET, equipment and materials, ET technique, possible risks and complications, training and competence. Specific aspects of the laboratory procedures are covered, in particular the different loading techniques and their potential impact on the final outcomes. Potential future developments and research priorities regarding the ET technique are also outlined.

Limitations reasons for caution: Many topics were not covered in the literature review and some recommendations were based on expert opinions and are not necessarily evidence based.

Wider implications: ET is the last procedural step in an ART treatment and is a crucial step towards achieving a pregnancy and live birth. The current paper set out to bring together the recent developments considering all aspects of ET, especially emphasizing US quality imaging. There are still many questions needing answers, and these can be subject of future research.

Study funding/competing interests: No funding. A.D.A. has received royalties from CRC Press and personal honorarium from Cook, Ferring and Cooper Surgical. The other co-authors have no conflicts of interest to declare that are relevant to the content of this article.

Keywords: ART; IVF; embryo transfer; good practice; pregnancy; recommendations; ultrasound.

Figure 1.

Flow chart of the selection of papers included in the narrative review of the technical aspects of embryo transfer. US-GET, ultrasound-guided embryo transfer.

Figure 2.

Recommendations regarding the requirements and preparations prior to embryo transfer. ET, embryo transfer; US, ultrasound; WG, working group.

Figure 3.

Recommendations regarding the embryo transfer procedure. ET, embryo transfer; WG, working group; OHSS, ovarian hyperstimulation syndrome; FET, frozen embryo transfer.

Figure 3.

Recommendations regarding the embryo transfer procedure. ET, embryo transfer; WG, working group; OHSS, ovarian hyperstimulation syndrome; FET, frozen embryo transfer.

Figure 4.

Recommendations regarding quality assurance and performance. ET, embryo transfer; KPIs, key performance indicators.

Figure 5.

List of items to be checked before embryo transfer. ET, embryo transfer.

Figure 6.

Patient information required on the patient records. ET, embryo transfer.

Figure 7.

Catheter loading methods used in human embryo transfer. (A and B) Air–fluid method: the transfer media containing the embryo(s) separated by air spaces on both sides. (C) fluid-only method: the embryo(s) is placed in a complete column of fluid without any air brackets or bubbles.

Figure 8.

Ultrasound images showing various factors related to a transabdominal ultrasound-guided embryo transfer. (A) Zoom window focused on the uterine cavity. (B) Deep field view of embryo transfer (ET) during catheterization. (C) Retroverted uterus ET. (D) ET catheter approaching the fundal part of the endometrium. (E) Measurement of distances between tip of catheter and fundal endometrium and between embryo bubble and endometrium. (F) Artefacts during ET: example of mirror image artefact (uterus is anteverted but there is a false image showing a retroverted uterus).