Oocyte euploidy, pronuclear zygote morphology and embryo chromosomal complement

Abstract

BACKGROUND: Pronuclear morphology has been proposed as an indicator of embryo development and chromosomal complement. In this study, the morphology of pronuclear zygotes generated from euploid oocytes [diagnosed by first polar body (PB1) analysis] was evaluated and compared with the configurations observed in chromosomally normal embryos (diagnosed by blastomere analysis). MATERIALS AND METHODS: Group 1-238 patients underwent 273 assisted conception cycles in combination with the screening of aneuploidy on PB1 for the chromosomes 13, 15, 16, 18, 21 and 22. Only normal oocytes were inseminated. Group 2-218 patients underwent 318 assisted conception cycles with aneuploidy screening on day 3 embryos. In both groups, oocytes were checked for fertilization and pronuclear morphology at 16 h after insemination. RESULTS: Seventy-three percent of zygotes from Group 1 had the configurations with centralized and juxtaposed pronuclei, large-size aligned or scattered nucleoli and PB located in the longitudinal or perpendicular axis of pronuclei. In Group 2, these configurations corresponded to those with the highest proportion of chromosomally normal embryos. Accordingly, in both groups, these configurations had a higher implantation rate than all the others. CONCLUSIONS: These observations confirm that some patterns of pronuclear morphology are associated with a higher proportion of euploidy and implantation reaffirming the relevance of this scoring system for the prediction of zygote viability.

A Bayesian network model for predicting pregnancy after in vitro fertilization

“…During the culture, each embryo is observed and graded once a day; the grade is assigned by assessing the morphology of the embryo according to state of the art criteria [22,3,2]. Embryos whose morphology meets several criteria are graded as top, namely they are expected to have higher probability of implantation (if transferred into a receptive uterus) than non-top ones.…”

“…Embryos are cultured for 2-5 days, before being transferred to the woman. During the culture, the morphology of each embryo is monitored at fixed time intervals; embryos with certain morphologies have indeed high implantation potential [1,2,3] and are thus graded as of top quality. Despite the effort for designing effective scoring system for the embryos [2], predicting blastocyst development remains a challenging problem [4], although promising results have been recently obtained by analyzing time-lapse embryo images collected by automated image monitoring systems [5,6].…”

The Role of Aneuploidy Screening in Human Preimplantation Embryos

“…Unfortunately, the morphological selection criteria for human gametes and embryos across all developmental stages have shown only weak correlations with aneuploidy (Munne 2006;Gianaroli et al 2007;Alfarawati et al 2011a). Karyotypic analysis indicates that there is a higher rate of chromosome abnormalities in morphologically abnormal monospermic embryos than morphologically normal embryos (Pellestor 1995;Almeida & Bolton 1996).…”

The Role of Aneuploidy Screening in Human Preimplantation Embryos

“…An indirect aneuploidy screening test was first explored by associations with conventional embryo morphology scoring. However, morphological embryo grading is apparently at its limits to improve IVF success rates and has only shown very limited correlation with aneuploidy (Munne 2006;Gianaroli et al 2007;Alfarawati et al 2011a). The implementation of time-lapse imaging to embryo culture has facilitated high resolution morphokinetic analysis of embryo development in an attempt to improve IVF success rates and eliminate potentially abnormally developing embryos.…”