Fertilization and early embryology: Morphometric parameters of living human in-vitro fertilization embryos; importance of the asynchronous division process

Abstract

A total of 304 human pronuclear zygotes and cleaved embryos from the 2- to 9-cell stages, obtained during invitro fertilization attempts, were photographed and retrospectively analysed after transfer for their morphology and size in relation to their developmental stage, using the Imagenia programme of a Biocom 500 image analyser. Morphometric parameters were calculated from the perimeters, surface measurements, theoretical diameters and circularity factors for the different structures analysed. This report provides the morphometric characteristics of living embryos. For the whole population the mean values were: 157.4 microns for the external zona pellucida diameter, 121.8 microns for the internal zona pellucida diameter, 17.9 microns for the thickness of the zona pellucida and 117.2 microns for the embryo cell mass diameter. The morphometric characteristics of the pronuclear-stage population were significantly different from the cleaved cell stages. If the zona pellucida and cell mass embryo diameters increased slowly from the 2- to 9-cell stages, embryonic external diameters were higher and zona pellucida thicknesses were lower in odd than even number blastomere embryos. Preliminary results show that in cases where implantation occurs, the embryo has a lower zona pellucida thickness. A comparison of the different embryo cell stages confirmed the existence of an asynchronous division process during early embryo development. Global results show no evidence of morphometric differences between subpopulations of the embryos according to their microscopic grading. Deviations from the normal asynchronous division process, however, appear to be a new parameter to take into account during embryo scoring.(ABSTRACT TRUNCATED AT 250 WORDS)

A minimally invasive methodology based on morphometric parameters for day 2 embryo quality assessment

“…From the results obtained in this study, embryos with a lower ZP thickness have a higher chance of successfully implanting. These results coincide with those proposed by the research group that studied ZP thickness and its relationship with embryo implantation morphometricly (Roux et al 1995). ZP thickness is associated with the embryo's ability to both develop and For the other morphometric variables analyzed, highly significant differences were observed only for the embryo measurements: area and roundness when they were compared in relation to implantation.…”

The association of the blastomere volume index (BVI), the blastomere symmetry index (BSI) and the mean ovality (MO) with ongoing implantation after single embryo transfer

“…But from a biological point of view, during the division from one to eight cells, some sort of asynchrony should be expected in three, five, six and seven cell embryos [17]. Therefore, the significant higher mean BSI in the evenly cleaved embryos compared to the unevenly cleaved embryos was expected.…”

“…Because embryos should have an asynchronous division process during early embryo development [17], we split the embryos into two groups for the BSI analyses: a group of unevenly cleaved embryos (3, 5, 6, 7, 9, 10, 11 and 12 blastomeres) and a group of evenly cleaved embryos (2, 4 and 8 blastomeres).…”

The impact of pronuclear orientation to select chromosomally normal embryos

“…3 Genetics Laboratory, São Paulo, S.P., Brazil. 4 Federal University of São Paulo, S.P., Brazil. to discard the pre-embryos is commonly based for existing non-invasive markers performed under low magnification at laboratories.…”

“…Several non-invasive strategies can be used to improve end-results: pronuclei disposition, nucleolar organization (1-3), assessment of cell number, the morphological appearance at the time of transfer, and identification of normal-cleaving embryos with only mononucleate blastomeres without fragmentation (4)(5)(6)(7)(8)(9).…”