PURPOSE: Our purpose is to describe the development of a blastocyst-stage embryo after the selective fertilization of a mature oocyte from a binovular zona pellucida by intracytoplasmic sperm injection (ICSI). METHOD: A 34-year-old woman underwent intracytoplasmic sperm injection due to severe male-factor infertility. After oocyte retrieval, a binovular zona pellucida including one mature metaphase II oocyte and one immature oocyte at the germinal vesicle stage as well as nine metaphase II oocytes was injected with spermatozoa using a one-to-one approach. RESULTS: The injected mature oocyte of the binovular zona pellucida showed fertilization as evidence by the presence of two pronuclei and cleaved to a four-cell embryo on the second day, while the uninjected oocyte showed signs of degeneration. On the third day, this embryo further cleaved to six blastomeres with slight fragmentation and it reached the blastocyst stage on the sixth day. CONCLUSIONS: Selective fertilization of one oocyte from a binovular zona pellucida by ICSI may lead to the development of a morphologically normal blastocyst-stage embryo which can be used for embryo transfer in the presence of a limited number of embryos.
PURPOSE: Our purpose is to describe the development of a blastocyst-stage embryo after the selective fertilization of a mature oocyte from a binovular zona pellucida by intracytoplasmic sperm injection (ICSI). METHOD: A 34-year-old woman underwent intracytoplasmic sperm injection due to severe male-factor infertility. After oocyte retrieval, a binovular zona pellucida including one mature metaphase II oocyte and one immature oocyte at the germinal vesicle stage as well as nine metaphase II oocytes was injected with spermatozoa using a one-to-one approach. RESULTS: The injected mature oocyte of the binovular zona pellucida showed fertilization as evidence by the presence of two pronuclei and cleaved to a four-cell embryo on the second day, while the uninjected oocyte showed signs of degeneration. On the third day, this embryo further cleaved to six blastomeres with slight fragmentation and it reached the blastocyst stage on the sixth day. CONCLUSIONS: Selective fertilization of one oocyte from a binovular zona pellucida by ICSI may lead to the development of a morphologically normal blastocyst-stage embryo which can be used for embryo transfer in the presence of a limited number of embryos.