The importance of the length of uterine cavity, the position of the tip of the inner catheter and the distance between the fundal endometrial surface and the air bubbles as determinants of the pregnancy rate in IVF cycles

Objective: To evaluate the relationship between the pregnancy rate (PR) and the positioning of the intrauterine catheter at embryo transfer (ET) under transabdominal ultrasound (US) guidance in in vitro fertilization (IVF) cycles. Study design: Prospective data analysis of 281 consecutive US-guided fresh ETs performed by a single physician at Yeditepe University Hospital IVF Center, Istanbul, Turkey, after controlled ovarian hyperstimulation between April 2012 and March 2013. The length of the uterine cavity (A), the distance between the fundal endometrial surface and the tip of inner catheter (B), the distance between the fundal endometrial surface and the air bubbles (C), and the pregnancy rates (PRs) were recorded. Results: The mean age of the patients was 33.25 +/- 5.5 years. Of all transfers, 115 (40.9%) resulted in a clinical pregnancy. With regard to distance (C), the clinical intrauterine pregnancy rates were 65.2%, 32.2% and 2.6% in the <10 mm, 10-20 mm, and 20 mm distance groups, respectively. The PR was dramatically reduced in cases with >10 mm between the fundal endometrial surface and the air bubbles, although this did not reach statistical significance. Between those patients who conceived and those who did not, there was no significant difference in terms of the distance between the fundal endometrial surface and the tip of inner catheter, the ratio of A/B or the ratio of B/C. Conclusions: The final position of the air bubble used as an identifier of the position of the embryo at ET can be determinative for PR, although it cannot be predicted. Clinical pregnancy rates appeared higher in cases with air bubbles closer to the fundus and the optimal position of the air bubble seems to be a distance of <10 mm from the fundal endometrial surface. It could be advisable to monitor the final position of air bubble at ET for identifying PR. In addition, the depth of uterine cavity may be considered to indirectly be important factor as it affects ET depth. The optimal distance between the fundal endometrial surface and the tip of inner catheter is 1.5-2 cm. Further well-designed randomized controlled trials are required to optimize ET technique in the future. (C) 2013 Elsevier Ireland Ltd. All rights reserved.