Comparative Analysis of Pregnancy Rates After the Transfer of Early Dividing Embryos Versus Slower Dividing Embryos

Abstract

Introduction: The goal of embryo selection is to be able to choose the embryo that will have the best chance of implantation and a successful pregnancy. Early division to the 2-cell stage is another easy and non-invasive method used to evaluate embryo viability. Design: A prospective comparative study. Objective: In this study the pregnancy outcome was compared in two groups of intracytoplasmic sperm injection (ICSI) patients, using the early division (26 hours post injection) to the 2-cell stage as a criterion for embryo viability and quality. Patients: One hundred and forty three patients undergoing routine ICSI cycles. Intervention: Routine culture of embryos in vitro with evaluations performed at 18h, 25–27h, 45h, and 72h for embryo cleavage and quality. The transfer of selected embryos into the fallopian tube or the uterus. Results: Early cleavage was observed in 44% (63/143) of the cycles included in the study. For group A (n=63), at least one “early dividing” was transferred and in group B (n=80), no “early dividing” embryo was transferred. When group A and B were compared, overall and ongoing pregnancy rates in group A were significantly increased when compared with that in group B [41.3% (26/63) vs 20.0% (16/80); p = 0.0069] and [33.3% (21/63) vs 16.3% (13/80); p = 0.0191] respectively. When the pregnancy outcome of the two transfer methods were compared, the tubal transfer route showed increased (but not significant) ongoing pregnancy rates in both group A and B [38.5% (15/39) group A and 22.7% (10/44) group B] when compared with uterine transfer [25.0% (6/24) group A and 8.3% (3/36) group B]. Overall pregnancy rates in uterine transfer cycles in group A were however significantly increased compared to group B [37.5% (9/24) and 11.1% (4/36) respectively; p = 0.016]. Our results also suggest that when early cleavage embryos (group A) are available, both tubal and uterine embryo transfers can be considered. When no early cleavage embryos (group B) are available, tubal transfer should be considered.