ORIGIN OF TRIPRONUCLEATE ZYGOTES AFTER INTRACYTOPLASMIC SPERM INJECTION

Zygotes morphologically classified as tripronuclear (3PN) after intrac ytoplasmic sperm injection (ICSI), which are thought to be digynic in their origin, were studied by fluorescent in-situ hybridization (FISH) . FISH results allowed us to assess the suspected ploidy after morphol ogical evaluation of the zygote and to determine the origin of the thi rd pronuclei, Our results show that, firstly, 36% of those zygotes cla ssified as 3PN following their morphological evaluation were, in fact, diploid, and secondly, the main cause for triploidy after ICSI is the non-extrusion of the second polar body.