Embryo transfer maneuvers and manipulations – the effect on in vitro fertilization (IVF) outcomes


      To determine the effect of maneuvers performed on the embryo transfer (ET) catheter during ET on in vitro fertilization (IVF) outcomes


      Retrospective cohort study.

      Materials and Methods

      This study included all women undergoing IVF/ICSI with a subsequent Day 3 or Day 5 ET at a single academic hospital IVF practice from 1/2013 to 1/2018. The first ET during the study period was included from each patient. A ‘trial followed by transfer’ method was routinely employed and all ETs were performed under abdominal ultrasound guidance. Each ET was systematically scored on ease by the transferring physician (easy, some difficulty, extreme difficulty) and any additional maneuver or instrumentation that was needed to perform the ET, such as bending the outer sheath of the catheter, extending the outer sheath over the inner catheter, and retaining the external sheath (conversion into an ‘afterload’ method).
      The primary outcome was live birth rate. Secondary outcomes included clinical pregnancy rate (CPR), implantation rate (IR), ectopic, biochemical and miscarriage rate.
      Direction of the uterus, catheter used, infertility diagnosis, BMI, age, donor egg, fresh versus frozen embryo, use of a gestational carrier, preimplantation genetic testing, endometrial thickness, presence of blood and mucus on the transfer catheter, distance from the fundus, and physician performing the ET (fellow or attending) were all tested as potential confounders in univariate analyses. Log-binomial models and Poisson regression models, adjusted for catheter used, presence of mucus, donor egg, and fresh versus frozen, were used to estimate the adjusted relative risks (ARR) with a 95% confidence interval. A stratified analysis, based on ease of ET, was performed.


      A total of 3,995 ETs were included (76% fresh, 24% frozen). Overall CPR was 46% and LBR was 36%. Twenty-six percent of ETs were performed with the afterload technique with a retained external sheath. A bend was placed in 37% of ETs, and the outer sheath was extended in 49% of transfers. The univariate analyses showed that a bent or extended sheath conferred no difference in outcomes, whereas the afterload technique conferred a lower live birth rate and clinical pregnancy rate (p=0.001). Amongst transfers that were easy or performed with some difficulty, the live birth rate with and without a retained sheath was 32% and 38%, respectively. Within the stratified model based on transfer ease, after adjustment for confounding, there was no significant difference in outcomes when ET catheter maneuvers were performed.


      Amongst ETs performed with ease, some difficulty, and extreme difficulty, there was no significant impact of bending the sheath, extending the sheath, or retaining the external sheath on cycle outcomes. However, there was a trend toward worse clinical pregnancy and live birth rates when the external sheath was retained, even amongst easy transfers. Consideration should be made in light of this finding for centers that use ‘afterload’ as their primary ET technique.