Developmental prognosis for zygotes based on pronuclear pattern: Usefulness of pronuclear scoring

Abstract

Purpose: To relate pronuclear patterns (PN) and zygote cytoplasmic appearance and embryo morphology.Methods: The usefulness of PN classification described by Tesarik et al. 1999 (patterns p0-5) and Scott et al. 2000 (Z1-4), for embryo selection is assessed.Results: Sinchrony on polarization and number of nucleolar precursor bodies (NPB) were associated with good quality embryos (p0 60.9% and p3 67.3%, and Z1 62.5% and Z2 64.7%; p < 0.01). Pattern 4 zygotes were associated with small number of NPB developed into multinucleated embryos (14.3%) and poor quality embryos (61.9%). No significant differences were found in the pregnancy rate between transfer of at least one good prognosis PN pattern and transfer of poor prognosis PN patterns, although 75% of the transfers included at least one embryo derived from a pattern 0 zygote, and 55% included embryos from categories Z1 or Z2.Conclusions: Sequential assessment involving the evaluation of oocyte quality, the classification of PN patterns and embryo morphology allows a more accurate evaluation of embryos to be selected for transfer.

Embryo quality but not pronuclear score is associated with clinical pregnancy following IVF

“…The assembly of NPB requires pronuclear chromatin and is indicative of the end of cell cycle phase G1 and the start of synthesis and processing of ribosomal RNA [20][21][22]. PN scoring in human IVF was originally reported as a predictor of embryo development [6,7,10,11].…”

“…Early literature supported the predictive power of PN scoring following IVF and ICSI. This includes a study of 787 embryos that reported PN scores predicted the rate of embryo development on day 3 [23], a 2007 study that observed PN patterns from 569 embryos predicted both good and poor quality embryos depending upon the pattern [20], and a study of 2,836 zygotes that showed PN scores were predictive of developmental ability on day 3 as well as implantation potential [24].…”

Does early cleavage correlate with chromosome constitution in human preimplantation embryos?

“…Ovarian stimulation (Barri et al, 2002) and laboratory procedures for gamete and embryo handling have been previously described (Arroyo et al, 2007). In all cases embryos were obtained by ICSI, cultured and biopsied according to our standard protocols.…”

“…Embryos at day 2 of development were scored according to morphological parameters such as cell number, symmetry, percentage of cytoplasmic fragmentation and blastomeres multinucleation. Two groups were considered: good morphology group (GM) which included embryos with at least 4 non-multinucleated blastomeres, symmetric or not, and ≤25% fragmentation, and poor morphology group (PM) which comprised embryos with either <4 symmetric or not blastomeres and/or at least one multinucleated blastomere and/or ≥30% fragmentation (Arroyo et al, 2007).…”

“…It has been suggested that the assessment of early cleavage is less subjective and more reliable, fast and simple to routinely apply in any laboratory, as opposed to the assessment of pronuclear morphology (Tesarik and Greco, 1999;Scott et al, 2000;Arroyo et al, 2007;Nicoli et al, 2013). Furthermore, with time-lapse methodologies, early cleavage is easier to assess (Rubio et al, 2012;Chamayou et al, 2013).…”