Objective: To compare implantation and pregnancy rates (PRs) achieved with blastocyst transfer (BT) and day 3 ET in similar patient populations.
Design: Retrospective analysis.
Setting: Academic infertility center.
Patient(s): One hundred consecutive patients <40 years undergoing IVF, each with more than three eight-cell embryos on day 3.
Intervention(s): Patients used their own eggs for IVF or IVF and intracytoplasmic sperm injection. Embryos were cultured in P1 medium (Irvine Scientific, Santa Ana, CA) until day 3, when they were either transferred or, in the case of embryos for BT, incubated in Blastocyst Medium (Irvine Scientific), followed by transferring on day 5.
Main outcome measure(s): Implantation and PRs.
Result(s): There were no statistically significant differences in patient age, FSH level, or number of oocytes or zygotes. The BT group had fewer embryos transferred (mean, 2.4) compared with the day 3-ET group (mean, 4.6). The viable PR (cardiac activity at 6-7 weeks was considered indicative of a viable pregnancy) was higher with BT (68%, 34/50) than with day 3 ET (46%, 23/50). The implantation rate was increased with BT (47%, 56 sacs/120 embryos) compared with day 3 ET (20%, 46 sacs/231 embryos).
Conclusion(s): The BT group in our study had higher implantation and PRs compared with the day 3-ET group. Better embryo selection, improved embryo-uterine synchrony, and decreased cervical mucus on day 5 may have accounted for the enhanced outcome. Our data support the use of BT to limit the number of embryos transferred while improving PRs.