Blastocyst versus cleavage stage embryo transfer policy. New aspects of an ongoing debate

L. Dracea, D. Codreanu, A. Coricovac, L. Mirzan, I. Boleac

Abstract: The aim of this study is to analyze the results of a new embryo transfer policy established in order to balance the learning curve effect and the challenges of starting a new in vitro fertilization (IVF) clinic. The ongoing debate regarding blastocyst versus cleavage stage embryo transfer policy becomes more complex when applied in a new clinic that introduced for the first time in Romania new technologies of assisted reproduction: extended culture to blastocyst stage and vitrification of blastocysts. Patients have been divided into two groups: those with embryos transferred at cleavage stage(group A) and patients with embryos transferred on day 5, at blastocyst stage (group B). Allocation of patients to cleavage stage or blastocyst embryo transfer has been based on a “all cleaved embryos or blastocyst” policy, witch means that we either transferred all cleaved embryos, if up to three, or we cultured the embryos to blastocyst stage, if more than three,including poor quality embryos. This policy comes in contrast to most programs that make a decision based only on good quality embryos. We made a comparative retrospective analyze of our data. We also present our first initial experience with vitrification of blastocysts. Results. Blastocyst formation rate was very high 47%, reflecting the optimal culture conditions. Implantation and pregnancy rates for blastocysts almost doubled when compared with cleavage stage embryos. Pregnancy rate was 62.20% for blastocyst transfers as opposed to 34.03% for cleaved embryos. The pregnancy rate for all cycles was 53.75%, extremely high for a starting program. The number of vitrified blastocysts transfers was not significant. Obtaining a good survival rate of blastocysts and afterward, a good pregnancy rate with vitrified blastocysts are the main outcomes. The policy of transferring either all cleaved embryos up to three or blastocysts is a safe and efficient policy which eliminates the negative effect of the learning curve in a new clinic that introduces new programs. Extended culture of embryos might improve the success rate when using an adequate incubation system. With our policy, the pregnancy rate is not affected by the selection of embryos at cleavage stage and is overall maximized. The significant difference in pregnancy rate between the two groups is related to the better implantation potential of blastocysts, but also to the worst prognosis of the cycles with few than four embryos obtained. Vitrification of blastocysts seems to be a simple, efficient and convenient freezing technique for a starting program. This study showed a pregnancy rate maximisation and cost and time reducing associated with slow freezing of a number of unviable embryos, being one of the first ongoing blastocyst transfers and pregnancies achieved with vitrified blastocysts which could open new future perspective in obstetric field.
Keywords: blastocyst, vitrification, in vitro fertilization, extended culture, starting program