P-513 Effect of embryo migration after embryo transfer with fresh oocyte donation cycles on pregnancy outcomes
Authors: Eraslan A , Gursu T , Goksever Celik H , Angun B , Yeh J , Bastu E 
Published: June 2023

Abstract

Study question
Is there any effect of embryo migration on clinical pregnancy rate and live birth rate in fresh oocyte donation cycles?

Summary answer
Clinical pregnancy rate and live birth rate were not affected from embryo migration in any direction.

What is known already
Embryo transfer is the final crucial step to affect success rates and up to date there has been vast amount of studies to optimize embryo transfer for better implantation and increasing clinical pregnancy rate and live birth rate. Embryos are loaded on the catheter mostly in the order of air-embryo-air-medium. By doing so, we indirectly visualize embryo(s) via air bubbles and we rely on bubble position as a reflector of embryo position. In literature, there are no studies investigating whether there is any embryo migration after 60 minutes of embryo transfer and the effect of this migration on pregnancy outcomes.

Study design, size, duration
The study included fresh oocyte donation (OD) cycles of recipient women. In vitro fertilization (IVF) cycles, frozen-thawed embryo transfer cycles, cryopreserved-thawed OD cycles were excluded.

Participants/materials, setting, methods
The migration distance was assessed by ultrasound twice, one of them immediately after embryo transfer (ET) and the second one at 60th minutes of ET. All embryos were expulsed to 10-20 mm from the fundus. The first group consisted of patients whose embryos migrated towards fundus, second group with embryos remained between 10 and 20 mm from fundus and the third group including embryos migrated towards cervix. Three groups were compared for pregnancy outcomes.

Main results and the role of chance
A total of 611 fresh OD cycles were recruited in this study. At 60 minutes after ET; in 123 patients (20.1%) embryos were located nearer than 10 mm to the fundus (Group 1), in 476 patients (77.9%) embryos were located at same initial expulsed zone (Group 2) and in 12 patients (2%) embryos moved more away from fundal endometrium towards cervix (Group 3). In group1, there were 96 clinical pregnancies (CPR:78.0%) and 78 live births (LBR: 63.4%). In group 2, CPR and LBR were 72.1% (n = 343) and 66% (n = 314), respectively. In group 3, there were 8 clinical pregnancies (CPR:66.7%) and all had live birth (LBR:66.7%). There was no significant difference in terms of CPR and LBR between the groups.

Limitations, reasons for caution
Our study is the first to search the impact of embryo migration on live birth rate in fresh OD cycles with high number of patients. Although our population had sufficient number of participants with analyzing LBR; we believe prospective designed studies are required.

Wider implications of the findings
Our study reveals that the concept of embryo migration is a fact and almost 20% of embryos migrate, whether towards fundus or cervix. On the other hand, whether embryo stayed static or migrated, CPR and LBRs are high in freshOD cycles, independent from any possible migration.

Trial registration number
NCT044855669