Demonstration of a mechanism of aneuploidy in human oocytes using Multifluor fluorescence in situ hybridization

Objective: To evaluate the potential of Multifluor fluorescence in situ hybridization (M-FISH) for karyotyping the human oocyte and first polar body. Design: Prospective case study. Setting: Research laboratories, university hospital. Patient(s): A 33-year-old woman with polycystic ovary syndrome who was undergoing ovarian stimulation and ICSI. Main Outcome Measure(s): Karyotyping of all chromosomes within an oocyte and first polar body, using GV stage oocytes matured to metaphase II in vitro. Result(s): Oocyte hyperploidy was diagnosed by M-FISH to be 23, X + 15 cht + 19 cht +22 cht. The corresponding polar body was hypoploid, with a karyotype of 23, X - 15 cht - 19 cht -22 cht. Ms was due to unbalanced predivision at meiosis I. Reprobing confirmed karyotype assignments for chromosomes X, 13, 18, and 21. Conclusion(s): The mechanism involved in maternally derived aneuploidy can be defined by using M-FISH to simultaneously karyotype both oocyte and first polar body chromosomes at metaphase II. Multifluor FISH may be useful for investigative studies of maternally derived aneuploidy, which is a major cause of preimplantation waste in natural and assisted reproduction. (Fertil Steril(R) 2001;76:837-40. (C) 2001 by American Society for Reproductive Medicine.).