O-039 Con - the faster the better

Abstract

Abstract Late o’clock: Are slow growing embryos clinically usable? Con - the faster the better Reproductive medicine and, within it, embryology, have experienced milestones in the understanding of pre-implantation embryonic development over the last quarter of a century. The development of blastocyst culture media for embryo culture even after embryonic genome activation and the possibility of continuous monitoring of embryonic morphokinetics throughout the pre-implantation period have been major contributors. The development of molecular genetic techniques has also played an important role. The introduction of new cryopreservation techniques has also improved the success rate of the clinical use of surplus embryos, including slow-growing embryos not otherwise selected for fresh cycle transfer. Two questions are most frequently encountered in clinical embryology today: which embryo in a cohort has the best chance of resulting in a live-born child, and how slow and morphologically suboptimal can an embryo be to still be considered clinically useful? In particular, the latter question does not have an easy answer, as embryos demonstrate varying pace of development. A further problem arises if there are no optimal embryos available in the cohort and this answer has to be given on day 2, 3 or 5, as this is when the embryo transfer is scheduled to take place. Some studies suggest that longer timing of any stage of embryonic development from pronuclear fading onwards means that the embryo is late in development due to certain abnormalities and is likely to be energetically depleted by the activation of its repair mechanisms. Such embryos not only have a lower implantation potential compared to fast embryos, but also diverge in time from the optimal receptivity of the endometrium. Additional testing and/or storage of slow-growing embryos brings the question of their clinical usability to the time of frozen embryo replacement cycles and quiets the couple's expectation of a “successful” completion of the stimulated cycle. Whether embryos are to be selected for fresh ET or FER, the “the faster - the better” principle is likely to be applied. In daily clinical practice, decisions on the use of slow-growing and/or morphologically sub-optimal embryos and the timing of embryo transfer are made on an individual basis, taking into account various medical as well as non-medical (e.g. economic, logistical) factors. These may also include portraying a positive image of the centre's performance. However, patients expect infertility specialists to make realistic assessments not only of the viability of slow growing embryos, but also of the outcome of the transfer of them. The assessment must be based not only on medical and ethical but also on rational grounds.