摘要：

STUDY QUESTION. To comprehensively evaluate and compare pregnancy and live birth rates following clinical touch, 2D, 3D or 4D ultrasound guided embryo transfer of a blastocyst. SUMMARY ANSWER. The use of 3D and 4D ultrasound is not superior to 2D transabdominal ultrasound, but all forms of ultrasound are superior to clinical touch alone. WHAT IS KNOWN ALREADY. While several factors contribute to the overall success of embryo transfer, the accurate placement of the embryo within the uterine cavity remains a critical determinant of implantation and subsequent pregnancy. While two-dimensional (2D) ultrasound provides basic imaging during embryo transfer, assisting with catheter placement, three-dimensional (3D) ultrasound adds volume and spatial information, aiding in assessing the endometrial cavity and embryo positioning. Meanwhile, four-dimensional (4D) ultrasound introduces real-time visualisation, offering dynamic insights into embryo movement and potential implantation. Although 2D remains a standard for most transfers, there is a growing interest in leveraging advanced imaging technologies to improve assisted reproductive outcomes. STUDY DESIGN, SIZE, DURATION. We searched bibliographical databases, including the Cochrane Central Register of Controlled Trials, EMBASE and Medline, from inception until August 2023. Randomised controlled trials that compared 2D transabdominal (2D TAUS), 2D transvaginal (2D TVUS), 3D and 4D ultrasound guided embryo transfer with one another or with clinical touch were included. The primary outcome was live birth rate (LBR), and the secondary outcome was clinical pregnancy rate (CPR) per transfer. PARTICIPANTS/MATERIALS, SETTING, METHODS. Two reviewers independently screened selected studies and extracted the data. Pairwise and network meta-analyses (NMA) were conducted according to the technique used. Effect estimates were odds ratio (OR) with 95% confidence interval (CI) for each outcome respectively. Summary estimates were calculated using random‐effects methods and quality assessment was performed using GRADE. MAIN RESULTS AND THE ROLE OF CHANCE. Twenty-eight trials, reporting data from 10,521 embryo transfer procedures, were included. Four different ultrasound modalities were evaluated: 2D transabdominal guided embryo transfer (2D TAUS) (21 trials), 2D transvaginal guided embryo transfer (2D TVUS) (four trials), 3D transabdominal guided embryo transfer (one trial) and 4D transabdominal guided embryo transfer (one trial). Compared to 2D TAUS, there was no difference in LBR in the network meta-analysis when using 2D TVUS (OR 1.14; 95% CI: 0.75-1.74), 3D ultrasound (OR 0.98; 95% CI: 0.49-1.97) or 4D ultrasound modality (OR 1.28; 95% CI: 0.56- 2.94). The use of clinical touch was associated with lower LBR (OR 0.71; 95% CI: 0.49-1.03). Compared to 2D TAUS, there was no difference in clinical pregnancy rate in the network meta-analysis when using 2D TVUS (OR 1.17; 95% CI: 0.86-1.58), 3D ultrasound (OR 0.97; 95% CI: 0.57-1.63) or 4D ultrasound modality (OR 1.30; 95% CI: 0.71- 2.38). The use of clinical touch was associated with lower CPR (OR 0.74; 95% CI: 0.64-0.85). LIMITATIONS, REASONS FOR CAUTION. Variability in study designs, methodologies, and participant characteristics across primary studies can complicate the synthesis of results. There was only one study directly comparing 3D and 4D interventions which resulted in sparse data, affecting the precision and reliability of estimates. WIDER IMPLICATIONS OF THE FINDINGS. Published evidence supports the continued use of 2D transabdominal ultrasound guided embryo transfer in routine clinical practice. There is insufficient evidence to support the introduction of 3D and 4D ultrasound when performing embryo transfers. Larger randomised controlled trials specifically assessing the superiority of these modalities are recommended. TRIAL REGISTRATION NUMBER. not applicable

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