Influence of Embryo Transfer Depth on in Vitro Fertilization and Embryo Transfer Outcomes

Objective: To investigate the influence of transfer distance from the fundus (TDF) on clinical pregnancy rate (PR) and ectopic pregnancy rate.

Design: Retrospective cohort. Between January 2000 and December 2001, 699 ultrasound (US)-guided embryo transfers were conducted. Mock transfer was performed to measure uterine cavity depth 1 month before treatment. Cavity depth was measured by abdominal US before the transfer, from the vaginal stripe to the fundus. Transfers were performed with a Wallace embryo transfer catheter (Cooper Surgical, Shelton, CT) using US and physician's judgment of cavity depth. Transfer distance from the fundus was calculated by subtracting the depth of catheter insertion from the cavity depth, as determined by US or by mock transfer. Statistical analyses were performed by building a multivariable logistic regression model to calculate odds ratios and 95% confidence intervals (CI).

Setting: Women aged 23 to 43 years who are in a university-affiliated, community-based IVF program in Springfield, Massachusetts.

Patient(s): All patients enrolled in IVF program undergoing embryo transfer.

Intervention(s): No patient received any additional procedure or intervention. All of the measurements obtained with the embryo catheter and the transvaginal ultrasound were part of the program's protocol for the embryo transfer.

Main Outcome Measure(s): Odds ratio examining relationship between embryo transfer depth and PR.Clinical, implantation, and ectopic PR were 37%, 20%, and 2.1%. Cavity depth by US differed from cavity depth by mock by at least 10 mm in >30% of cases. The TDF by US was highly predictive of PR; TDF by mock was not predictive of PR. Increasing the TDF by US resulted in significantly increased PR as well as lower ectopic rates. Using regression analysis, the odds ratio for TDF by US was 1.11 (95% CI: 1.07-1.14). This suggests that for every additional millimeter embryos are deposited away from the fundus, the odds of clinical pregnancy increased by 11%.

Conclusion(s): After controlling for potential confounders, the clinical PR is significantly influenced by the transfer distance from the fundus. Cavity depth by US is clinically useful to determine the depth beyond which catheter insertion should not occur.