Effect of embryo transfer catheter on implantation rates

Abstract

Objective: While changes in our IVF culture system had resulted in significant improvements in embryo quality, these improvements did not translate into improvements in pregnancy and implantation rates. The influence of the embryo transfer catheter upon pregnancy has been investigated in a number of previous studies, but with no consistent conclusions. The aim of the present investigation was to determine whether, in our system, the embryo transfer catheter affected pregnancy outcome. Design: A randomized, prospective comparison of the pregnancy rates with the currently-used catheter (Tomcat) and with another commercially available transfer catheter (SIVF 6019 catheter, Cook, Australia) in the period September to December 2001. Materials/Methods: Included in the evaluation were patients who met the following criteria: female partner <40 years of age, ≤2 previous IVF attempts, and with sufficient Day 3 embryos to meet the standard number to be transferred for each age group (irrespective of quality). All eligible patients were included, regardless of the etiology of their infertility or the treatment (i.e. IVF, ICSI or MESA). Pregnancy and implantation results (# sacs/total # embryos transferred) were compared using Fisher’s exact test. Results: A total of 118 Day 3 embryo transfers were included, 58 using the original catheter and 60 using the Cook catheter. The patients’ ages in each group were similar (33.6 vs 33.4 years, respectively), the average number of embryos transferred per patient was 2.7 and 2.8, and overall embryo quality was similar in both groups (31/58 vs 30/60 patients had only good quality embryos transferred). The pregnancy rates per embryo transfer were 16/58 (28%) and 31/60 (52%) (p <0.01), with implantation rates of 23 sacs/154 embryos (15%) and 52 sacs/170 embryos (31%), respectively (P <0.001). When only the younger patients (<35 years) were considered, the pregnancy rates were 7/32 and 17/35 (22% vs 49%; p <0.05) and the implantation rates were 11 sacs/68 embryos (16%) and 25 sacs/78 embryos (32%), respectively; p <0.05. Considering only patients who had exclusively 8-cell embryos transferred (40/58 and 41/60 patients, respectively), the pregnancy rates were 10/40 (25%) and 25/41 (61%; p <0.01). In this group, the mean numbers of embryos transferred were 2.0 and 2.1 per patient, giving implantation rates of 14 sacs/94 embryos (15%) and 40 sacs/101 embryos (40%; p <0.0001). Conclusions: The embryo transfer catheter was found to exert a significant effect upon the success of IVF treatment. The quality of the Day 3 embryos transferred during this study was high, as demonstrated by the high pregnancy and implantation rates achieved with the Cook catheter. These results serve to illustrate (a) the vital importance of controlling all aspects of embryo culture and transfer; and (b) the effect that a single adverse factor can have on the achievement of pregnancy.