LOW AND SLOW, SMOOTH AS SILK: EMBRYO PLACEMENT, TRANSFER VELOCITY AND AVOIDING CERVICAL TRAUMA PREDICT EMBRYO TRANSFER SUCCESS

Abstract

The objective of this study was to use the embryo transfer simulator to identify components of the embryo transfer technique that influence pregnancy and live birth rates. Institutional Review Board approval was obtained. Retrospective data were collected for all embryo transfers performed at a single urban medical center from 1/2015 to 1/2020. Subsequently, prospective data was accrued using a brief questionnaire along with the embryo transfer simulator. There were 14 enrolled physicians who each performed 25 simulated embryo transfers. Embryo transfer technique was compared between physicians and was then correlated to pregnancy outcomes from transfers performed in the previous 5-year period. Data collected included: management of cervical mucous, traversing the cervical canal with the inner catheter completely retracted (vs. extended), transfer distance from the fundus, number of fundal touches, duration of embryo transfer, time navigating the cervical canal, velocity of embryo expulsion, time stayed after embryo expulsion, and total score on embryo transfer simulator. A generalized estimating equation was used to examine the relationship between embryo transfer technique and pregnancy outcome, while controlling for multiple transfers by the same physician and confounders (e.g., age, BMI, PGT). There were 14 physicians enrolled, with an average age of 47.5 (SD 12.6) years and average of 13.5 (SD 12.4, range 0-35) years since fellowship graduation. There were significant differences in embryo transfer technique between physicians for nearly all variables of interest. The duration of embryo transfer on the embryo transfer simulator and stylet usage were significantly associated with decreasing live birth rates, aOR 0.995 (95% CI 0.990-1.00) and 0.440 (95% CI 0.256 -0.756). Traversing the cervical canal with the inner catheter completely retracted was associated with a decreased odds of pregnancy but not lower live birth rates, aOR 0.551 (95% CI 0.321-0.949) and 0.580 (95% CI 0.335-1.00). The transfer distance to the fundus and the velocity of embryo expulsion on the embryo transfer simulator were significantly associated with the odds of ectopic pregnancy aOR 0.457 (95% CI 0.247-0.879) and 1.302 (95% CI 1.035-1.642). This study confirmed that significant differences in transfer technique exist between physicians. Key components of the embryo transfer were identified that could be improved upon to positively impact pregnancy and live birth outcomes. Factors that decreased intrauterine pregnancy rates included long transfer duration, use of stylet, traversing the cervical canal with the inner catheter retracted, placing the embryos high in the fundus and high velocity of transfer.