Insights on blastomere nuclearity

Abstract

Purpose: To analyze the results of our transferred embryos, especially those that "changed" their blastomere nuclearity from Multinucleated (MN) to Mono-nucleated during development.Methods: Pregnancies where at least one MN embryo was transferred were retrospectively evaluated and categorized in order to record and follow-up on the ones that were implanted. Embryos were classified as normal (when all blastomeres were mono-nucleated on day one and two of development), corrected (multinucleated embryos on day one that became mono-nucleated on day two) and non-corrected (multinucleated either on day one, on day two or both days).Results: There were 633 transfer cycles analyzed. Thirtythree percent (206) had at least one embryo with a MN blastomere at a given stage of development. Pregnancy and implantation rates were 29.0% and 19.0% for the group of exclusively mono-nucleated embryo transfers, and 28.6% and 15.8% for the group with at least one MN embryo transferred. The pregnancy outcome for "corrected" and "noncorrected" embryos could be corroborated unequivocally in only 9 cases, with an outcome of 8 and 4 normal babies, respectively.Conclusions: Because the amount of data analyzed is not satisfactorily large, differences were not significantly different; however, a trend may exist showing that normal at term pregnancies obtained from corrected embryos are more likely to occur than those from non-corrected embryos. Nuclear observation on a daily basis should be one of the strate-Clínica de Fertilidad, Centro Médico Docente La Trinidad, Caracas, Venezuela e-mail: mgilco@cantv.net gies used to select the best embryos for transferring, to improve implantation rates and avoid multiple pregnancies.

The association between multinucleated blastomeres and poor ovarian response under the Bologna criteria

“…The literature is consistent with the fact that the rate of MNB is reduced on day 3 as compared to that on day 2 [5,7]. This has been explained due to a self-correction phenomenon [34,35] or due to the larger dimensions of day 2 blastomere size; their better optical accessibility and less cell overlap [5]. However, since the majority of cases and embryos (87 and 90 %, respectively) in the study were examined on day 2, it does not seem to have a major impact on our findings.…”

“…Since MNB is a dynamic phenomenon, one observation of embryonic growth can miss part of MNB detection [32,33]. Conversely, early cleaved embryos have been shown to have the ability of selfcorrection from multinucleated to mononucleated during development, and this occurrence could be missed when employing a single inspection [34]. Nevertheless, since all embryos in both the study and control groups were similarly examined, this limitation does not seem to significantly alter our main finding that MNB is more prevalent in POR cases.…”

Nucleation status of Day 2 pre-implantation embryos, acquired by time-lapse imaging during IVF, is associated with live birth

“…The concept of self-correction has also been supported by FISH (fluorescence in situ hybridisation) studies, suggesting the restoration of ploidy during early pre-implantation development [ 55 , 56 ]. The transient process of NE reversibility might also involve rearrangement of chromosomal anomalies [ 57 – 59 ] leading to mononucleated blastomeres at the four-cell stage [ 60 , 61 ] and subsequent successful deliveries [ 57 , 58 , 60 ]. The nucleation errors present in the 2-cell stage, even if corrected in the 4-cell embryo, maybe evident in the quality of blastocysts.…”

Embryo multinucleation at the two-cell stage is an independent predictor of intracytoplasmic sperm injection outcomes

“…Moreover, this long time could be needed to allow functional repair mechanisms. Previously it has been proposed that there could be a rearrangement phenomenon of chromosomal anomalies (32,34,35), thus explaining how MNB 2cell embryos can lead to mononucleated blastomeres at the four-cell stage (33,36) and successful deliveries (33)(34)(35). This phenomenon probably needs time to take place.…”

“…In the present study they accounted for 36.7% of the transferred embryos included (and 36.8% of these were multinucleated in both blastomeres). In addition, some of these retained the ability to develop to term (10,19,32,33). Consequently, it would be difficult in practice to reject all of these for ET.…”