Chromosomal status of uni-pronuclear human zygotes following in-vitro fertilization and intracytoplasmic sperm injection

Uni-pronuclear embryos (n = 42) were analysed by fluorescencein-situ hybridization (FISH) with two to four chromosome pair-specificprobes. Half of these embryos resulted from conventional inseminationand half from intracytoplasmic sperm injection (ICSI). The majorityof uni-pronuclear embryos from conventional insemination werenormally diploid (61.9%) whereas only 9.5% of uni-pronuclearICSI embryos (P < 0.001) were diploid. In addition, a significantlyhigher number of uni-pronuclear embryos from conventional inseminationhad a Y chromosome (10/21, 47.6%) when compared with ICSI embryos(2/21, 9.5%) (P = 0.015). It is concluded that the majorityof uni-pronuclear embryos following regular in-vitro fertilizationare fertilized, whereas those from ICSI are parthenogeneticallyactivated. The latter embryos should not be considered for embryoreplacement.