CARE Fertility has investigated the incidence and impact of vacuolation from time-lapse images acquired by the EmbryoScope (FertiliTech, Denmark). If not already present, the time of vacuole appearance varied greatly; vacuoles first presented between 0.35 hpi and 81.4 hpi (unpublished). Of 23 transferred embryos that had vacuolation recorded as present, nine resulted in ongoing clinical pregnancy. Nevertheless, embryos resulting from oocyte with vacuolation or developing vacuolation during their in vitro development are avoided for transfer where possible. Video 16.1 shows vacuoles developing in blastomeres at 60 hpi. The video can be viewed online: http:// goo.gl/bS9bkJ.