Extended embryo culture up to 14 days
Medicina Reproductiva y Embriología Clínica 17 June 2022 In press.
Introduction: The early stages of human embryonic development prior to implantation have been extensively studied to improve reproductive outcomes. However, subsequent events are unknown. In vitro advances have allowed extended culture of embryos up to day 14, considered the legal limit. We aim to review aspects related culture conditions, morphogenesis events, potential applications of extended culture of human embryos as well as some ethical issues surrounding this topic. Materials and methods: This literature review was carried out using different databases and websites by screening articles. Results and discussion: Extended culture consists of culturing embryos up to day 14 of development. This requires specific culture conditions of temperature and gas concentration, as well as a medium composition that is different from that used in clinical practice in IVF laboratories. In addition to having made it possible to document in vitro the morphological events and structures of the embryo after implantation, the study of mosaic embryos at these hitherto hidden stages could provide valuable information for clinical practice. All this has been achieved within the 14-day limit, but due to scientific progress this can be considered restrictive and different reasons have been put forward why it should be extended. Conclusions: Although prolonged culture has provided a better understanding of the events occurring between implantation and gastrulation, culture conditions must be improved to optimise the technique, and once this is achieved, consideration should be given to extending this limit. Furthermore, alternatives to the use of embryos, such as the development of embryos from stem cells, should be further explored. All of this could have a future clinical application in terms of choosing the best embryos or finding out about diseases that affect pregnancy and lead to miscarriage