Elective single embryo transfer (ESET): does the number of morhologic good cleavage embryos on day 2 affect outcome?

Abstract

After more than 3 decades since the birth of Louse Brown, the definition of success in infertility treatment has changed dramatically. Today, quality of IVF is measured on three criteria; 1) term birth, 2) birth weight and 3) singleton pregnancy. These goals can only be achieved by performing embryo transfer of one selected embryo at a time, preferably at the blastocyst stage. For those reasons, it is utterly important to have well defined criteria in place to determine which patients should be pushed to day 5 for an eSET. Therefore, we examine if the number of good quality cleavage stage embryo available on day 2 has on impact on the baby-take-home rate after eSET. Retrospective analysis. A total of 1545 eSETs were performed from February 2007 to February 2016. The average maternal age was 32±3.2yrs. Oocytes had undergone ICSI and cultured in single step media (Global) for extended culture under low oxygen tension (5%). eSETs were divided in four groups based on the number of available good cleavage stage embryos on day 2 defined as 4-cell stage embryos without fragmentation. The 4 groups were compared in terms of baby-take-home rate. Chi square test was used for statistical analysis of the data. There was no significant difference among the groups in regards to patient’s age, clinical pregnancy, implantation or baby-take-home rate. Regardless of the mean number of day 2 embryos, in all groups about 50% were vitrified at the blastocyst stage. Even the ratio between day 5 and day 6 vitrified blastocysts was similar in all groups.Tabled 1No. of good cleavage stage embryos on day 21-56-89-12>13No. of eSETs245430468402Age (Mean±SEM)32.4±3.232.3±3.331.8±3.231.5±3.1Mean number of day 2 embryos471017Mean number of blastocysts vitrified2358Total number of blastocysts vitrified433125122503159% Ratio of day 5 vs. day 6 vitrified68 vs. 3267 vs. 3366 vs. 3471 vs. 29Clinical pregnancy/eSET (%)54.3a55.1a56.5a52.5aImplantation rate (%)62a62.1a63.2a62.2aBabe-take-home rate (%)54.3a55.1a55.5a52aSets of Monozygotic twins (n)7345Live births (n)133237260209aχ2, P<0.05 Open table in a new tab aχ2, P<0.05 Our study found that when there are 5 or less day 2 good morphologic embryos, the patient can be confidently pushed to a day 5 eSET. The cryopreservation utilization rate was similar among the groups. Overall, stimulation toward lower egg numbers and in turn to less cleavage stage embryos provides a safe opportunity for the embryology laboratory to push patients under age 35 for an eSET. Along with the low number of multiple births, this approach delivers a high pregnancy rate, moving towards the endpoint of a single, safe and healthy live birth.