Background: Embryo transfer (ET) is a vital part of the IVF process. While some studies have supported the hypothesis that ET difficulty alters success rate, others suggest the contrary. This large population study aimed to test this hypothesis, using a standardised ET grading system.
Methods: ET data for fresh and frozen IVF/ICSI cycles between 2005 and 2010, retrieved from the IVFAustralia database, were grouped by degree of difficulty (easy, medium and difficult). Live birth rates, as the primary outcome, were compared between the groups. Biochemical pregnancy, Clinical Pregnancy Rate (CPR) and other pregnancy outcomes were assessed. The influence of blood ± mucus contamination on the transfer catheter tip and the use of intra-transfer ultrasound (US) were also analysed.
Results: Of 6484 transfers, 5976 (92.2%) were considered easy, 374 (5.7%) medium and 134 (2.1%) difficult. Basic patient characteristics were similar between the cohorts. There were statistically significant differences in the live delivery rates (25.3% vs 19.5%, p < 0.05), CPR (30.7% vs 24.6%, p < 0.05), and + ve βhCG rate (35.9% vs 28%, p < 0.05) between the easy and medium/difficult groups. There was no significant difference in the rates of ectopic pregnancy, stillbirth and miscarriage between the groups. The presence of blood on the catheter did not affect pregnancy outcome adversely (p = ns).
Conclusion: This study, which we believe to be the largest report using a standardised system for grading the difficulty of ET, demonstrates that difficult ETs are associated with lower live birth rates but not higher rates of ectopic or miscarriage. While the presence of blood may be an indicative of a relatively more traumatic and difficult transfer, it does not necessarily lead to a lower birth rate.