Transfer Technique - Seeing where you are going

The main variables that affect nidation are related to uterine receptivity, embryo quality and the efficiency of embryo transfer. Embryo transfer is the critical step in assisted reproductive technology; with rigid catheters, contamination with blood, mucus or bacteria, increased contraction waves of the myometrium, and the level of difficulty in introducing the catheter inside the uterine cavity tending to reduce embryo implantation rates (1-9). Little attention has been paid to embryo transfer, a fact reflected in the scientific publications regarding this subject, which are rare compared with those evaluating other aspects of IVF. The probable reason is the apparent simplicity of this maneuver, since most clinicians do not consider inserting a catheter through the uterine cervix and ejecting embryos a difficult task. This facility, however, is relative. Differences in individual transfer performances are reflected in the results reported in the literature. Meldrum et al. (10) and Naaktgeboren et al. (11) emphasized that meticulous embryo transfer is essential for the success of IVF. Assessing the question of the operator within the same program, Hearns-Stokes et al. (12) found significant differences in pregnancy rates between 11 clinicians who performed 854 embryo transfers. In that study, all aspects of the IVF-embryo transfer cycle were standardized: the groups were homogenous in terms of all aspects including embryo quality, the number of embryos transferred and the transfer technique employed. Karande et al. (13) reported significant differences in pregnancy rates between clinicians even when uniform protocols of ovarian stimulation and embryo culture were used. Embryos are routinely transferred through the transcervical route, with the catheter being inserted in two ways: blindly by ‘clinical touch’ or guided by ultrasound. Many services use the ‘sensitivity’ of the clinician to place the embryos within the uterine cavity at a point close to the fundus (4, 14), similar to the description published by Edwards more than 20 years ago. With respect to this type of embryo transfer, which is more traditional, no attempt has been made to document the variables that might have a negative impact and cause low pregnancy rates and failure of the whole process, such as inadvertent touch of the catheter tip on the fundal endometrial surface or inappropriate embryo placement in the uterine cavity (6-8,15).