Objective: To review the literature on the variables affecting embryo transfer success or failure and to define technical factors associated with optimal outcome.
Design: Literature review.
Results: Avoidance of blood, mucus, bacterial contamination, excessive uterine contractions, and trauma to the endometrium is associated with optimal pregnancy and implantation rates after transcervical embryo transfer. A trial transfer, ultrasonographic guidance, and use of "soft" catheters appear to facilitate successful embryo transfer.
Conclusion: An understanding of the variables associated with embryo transfer success together with adherence to techniques shown to facilitate atraumatic embryo transfer will enhance the efficiency of IVF by maximizing embryo implantation.