What is a difficult transfer? Analysis of 7,714 embryo transfers: the impact of maneuvers during embryo transfers on pregnancy rate and a proposal of objective assessment.

OBJECTIVE

To establish the relationship between the degree of difficulty of ET and pregnancy rate (PR), with a view to proposing an algorithm for the objective assessment of ET.

DESIGN

Retrospective, observational study.

SETTING

In vitro fertilization unit.

PATIENT(S): Women undergoing assisted reproductive technology (ART) with ET after IVF/intracytoplasmic sperm injection, in whom fresh embryo transfer or frozen-thawed embryo transfer was performed.

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): Clinical pregnancy rate (CPR).

RESULT(S): A total of 7,714 ETs were analyzed. The CPR was significantly higher in the cases of easy ET compared with difficult ET (38.2% vs. 27.1%). Each instrumentation needed to successfully deposit the embryos in the fundus involves a progressive reduction in the CPR: use of outer catheter sheath (odds ratio [OR] 0.89; 95% confidence interval [CI] 0.79-1.01), use of Wallace stylet (OR 0.71; 95% CI 0.62-0.81), use of tenaculum (OR 0.54; 95% CI 0.36-0.79). Poor ultrasound visualization significantly diminish the CPR.

CONCLUSION(S): The CPR decreases progressively with the use of additional maneuvers during ET. An objective classification of the instrumentation applied during ET is proposed.