Middle to Lower Uterine Segment Embryo Transfer Improves Implantation and Pregnancy Rates Compared with Fundal Embryo Transfer

Objective: To assess differences in pregnancy and implantation rates as a function of the embryo placement.

Design: Prospective cohort study.

Setting: A tertiary care center.

Subject(s): All fresh, nondonor IVF cycles performed in 2001.

Intervention(s): Alteration in embryo transfer (ET) target location from the fundal region to the middle to lower uterine segment.

Main Outcome Measure(s): Clinical pregnancy rate (sonographic sac evidence/number of transfer cycles), implantation rate (number of sacs/number of embryos transferred), patient age, peak E(2), and fertilization rate.

Result(s): A total of 393 fundal and 273 lower to middle uterine segment ETs were performed. The pregnancy (PR), implantation, and birth rates were significantly higher after a middle to lower uterine segment ET compared with fundal ET (39.6% vs. 31.2%; 21% vs. 14%; and 34.1% vs. 26.2%, respectively). Groups did not differ regarding patient age, basal FSH, peak E(2), number of intracytoplasmic sperm injection (ICSI) cycles, fertilization rate, embryo quality, or number of embryos transferred.

Conclusion(s): Both PR and implantation rates are favorably affected by directing embryo placement to the lower to middle uterine segment. By some unknown mechanism, it appears that this endometrial location provides a more favorable region for embryo deposition.