The degree of difficulty of embryo transfer is an independent factor for predicting pregnancy.

Background: The role of embryo transfer as regards the success of IVF/ICSI treatments is recognized but has not been comprehensively evaluated. In order to determine its importance, the degree of difficulty of 4807 embryo transfers after IVF/ICSI was analysed retrospectively.

Methods: Logistic regression analysis identified the age of the subject, type of treatment (IVF versus ICSI), number of embryos transferred and degree of difficulty of embryo transfer as independent factors predicting pregnancy. The main focus of the study was to evaluate the importance of the difficulty of embryo transfer after taking into account the other confounding variables.

Results: Embryo transfer was classified as easy (2821), intermediate (1644) or difficult (342). The transfer was considered difficult if it was time consuming, the catheter met great resistance, there was a need to change the catheter, if sounding or cervical dilatation was needed or if blood was found in any part of the catheter. Easy or intermediate transfers resulted in a 1.7-fold higher pregnancy rate than difficult transfers (P < 0.0001; 95% confidence interval: 1.3-2.2).

Conclusions: This study demonstrates that the degree of difficulty of embryo transfer is an independent factor as regards achieving pregnancy after IVF/ICSI. All efforts should be made to avoid difficult embryo transfers. Physicians should be alert to the factors associated with embryo transfer and should be instructed to use a stepwise approach in difficult transfers.