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Lookup NU author(s): Professor Mary Herbert
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Conventional practice in in vitro fertilization or intracytoplasmic sperm injection is to select the best quality embryos based on their morphology and cleavage status from a cohort of fertilized oocytes in which two pronuclei were observed at the time they were checked for fertilization. However, in a small proportion of cycles, the selection is limited to embryos that appeared to be either unfertilized (displaying zero pronuclei) or abnormally fertilized (displaying one or three pronuclei) at the time they were checked for fertilization. There is a lack of consensus on whether such embryos should be transferred to the uterus. Cytogenetic analysis of embryos from oocytes with one pronucleus has shown a proportion is diploid. Transfer of such embryos has resulted in healthy births. Limited cytogenetic analysis of oocytes that divide despite the absence of pronuclei at fertilization check indicates that a proportion also have a normal cytogenetic constitution. Cytogenetic analysis of embryos from oocytes with three pronuclei has shown high rates of triploidy and chaotic cell divisions. Subsequent foetuses have extremely unfavourable outcomes. Here, we review the published literature on the cytogenetic analysis of 'unfertilized' and 'abnormally fertilized' embryos and discuss possible pathways which lead to their formation. The limited evidence indicates that oocytes with one pronucleus and oocytes that show normal onward division despite the absence of pronuclei may be considered for replacement in certain circumstances.
Author(s): Feenan K, Herbert M
Publication type: Review
Publication status: Published
Journal: Human Fertility
Year: 2006
Volume: 9
Issue: 3
Pages: 157-169
ISSN (print): 1464-7273
ISSN (electronic): 1742-8149
URL: http://dx.doi.org/10.1080/14647270600636269
DOI: 10.1080/14647270600636269
