Ultrasound guided embryo transfer: summary of evidences to close the open debate. Literature review and meta-analysis

Aims. To collate all available evidence regarding the application of ultrasound techniques during embryo-transfer (ET). Through a meta-analytic assessment of randomized trials, comparing trans-abdominal ultrasound guided ET (TA-US ET) versus clinical touch (CT ET), we evaluated possible improvement in implantation, clinical pregnancy and ongoing pregnancy/live birth rates and associated reduction of ectopic pregnancy and miscarriage rates. Method. A systematic literature search and meta-analysis (English written literature) was conducted. The literature search yielded 1522 publications. 32 manuscripts were available for the systematic review of which 12 for meta-analysis. Articles were included only if they reported evaluable data of TA-US guided ET compared to CT on: i) implantation-rate; ii) clinical pregnancy-rate; iii) ongoing pregnancy-rate/live birth-rate; iv) miscarriage-rate; v) ectopic pregnancy-rate. Results. Meta-analysis demonstrated that implantation rate (OR 0.71, p<0.001;CI 95% 0.63-0.81,I2 0%), clinical pregnancy rate (OR 0.77,p<0.01; CI 95% 0.69-0.86,I2 52%) and ongoing/live birth rate (OR 0.84, p<0.05;CI 95% 0.72-0.97,I2 62%) were all reduced with CT ET compared to TA-US ET. This analysis found no statistically significant differences between CT ET versus TA-US ET for miscarriage and ectopic pregnancy rates. Conclusion. The effect of TA-US ET on clinical pregnancy rate, implantation rate and ongoing pregnancy are mildly positive. Considering that ultrasound scan is a wildely available and cost-effective tool in gynecology and human reporduction field its routine introduction during ET appears to have more benefits than disadvantages. Further studies are needed, indeed, to better understand potential value of this technique in other clinical outcomes such as ectopic pregnancy rate.