UNDOCUMENTED EMBRYOS - DO NOT TRASH THEM, FISH THEM

Pronuclei formation is routinely assessed 16-20 h after oocyte insemin ation in in-vitro fertilization (IVF). Occasionally, the pronuclei dis appear before this time, rendering them as 'undocumented'. Since the n umber of pronuclei detected is used to distinguish normal from abnorma l embryos in the context of ploidy, the diploidy of undocumented embry os is questionable, and therefore they are routinely discarded. The in troduction of fluorescent in-situ hybridization (FISH) technology allo ws the assessment of ploidy status in undocumented embryos that contin ue to cleave to form blostomeres. In this study, we wed FISH to analys e the chromosomal status of 23 undocumented embryos obtained from 10 p atients. Biopsied blastomeres were fixed and probed for five chromosom es (X, Y, 13, 18, 21). Diploidy was confirmed in 13 (57%) embryos whil e the remaining 10 embryos displayed various chromosomal anomalies. Si x of the diploid embryos were transferred subsequently to the patients . One ongoing pregnancy was achieved following transfer of an undocume nted, analysed embryo, which was already cleaved when assessed 20 h af ter insemination. We suggest that accelerated dismantling of the pronu clear membrane and subsequent cleavage do not necessarily indicate abn ormal chromosomal content and may result in normal pregnancy. In a pat ient with a small number of embryos, FISH may be used to ascertain dip loidy of undocumented embryos, thereby increasing the number of availa ble embryos for transfer.