Chromosomal complement and clinical relevance of multinucleated embryos in PGD and PGS cycles

Abstract

The objective of this retrospective study was to investigate the incidence and clinical implications of multinucleation in blastomeres biopsied from cleavage-stage embryos obtained from patients undergoing preimplantation genetic screening (PGS) for aneuploidies or preimplantation genetic diagnosis (PGD) for translocations or single-gene defects (SGD). A total of 3515 embryos were obtained from 306 couples in 380 PGD or PGS cycles. Incidence of multinucleation, chromosomal complement in multinucleated (MN) and sibling embryos and the characteristics of MN embryos resulting in healthy births were investigated. Of all cycles, 41.3% involved at least one MN embryo. There were more uniformly diploid than uniformly haploid nuclei (22.0% versus 7.9%, P<0.01). The most common form of abnormality was chaotic chromosomal complement (39.9%, 147/368). Transfer of embryos that had MN blastomeres free of the genetic abnormalities tested resulted in three healthy deliveries. It is concluded that, although the majority of MN blastomeres are chromosomally abnormal, healthy births are possible after transfer of embryos containing these blastomeres subjected to genetic analysis. As far as is known, this is the first report of healthy births after transfer of embryos with MN blastomeres tested for translocations or SGD in PGD cycles. Preimplantation genetic diagnosis (PGD) is an established method for selecting genetically healthy embryos for transfer. A blastomere sampled from the developing embryo is subjected to genetic analysis. Some of these blastomeres may contain multiple nuclei, complicating the genetic diagnosis. We investigated clinical implications of multinucleation in PGD cycles. Our results indicate that majority of the multinucleated blastomeres, and consequently embryos, are genetically abnormal. However, healthy births are possible after transfer of multinucleated embryos that are free of the genetic abnormalities screened.

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

“…Age was not found to affect MNB occurrence in our analysis. The same has been also reported by other investigators [14,17,25]. This may imply that MNB occurrence, similar to ovarian reserve studies (AFC and AMH), is a more appropriate Bbio-marker^of ovarian reserve than age.…”

“…Furthermore, several studies have shown that MNB is largely associated with an increased rate of aneuploidy and chromosomal abnormalities [1,4,16,17,[27][28][29][30][31]. Oocyte chromosomal abnormality is believed to be the main cause of low fertilization, cleavage, and implantation rates in POR cases, demonstrating high incidence of human embryo incompetence leading to low pregnancy and high abortion rates in these women.…”

“…Blastomere nuclearity was also incorporated into evidence-based integrated morphology cleavage embryo score for implantation potential of day 2 embryos in an ART setting [15]. Furthermore, several reports have shown that MNB has a relation to chromosomal integrity of the 2-4 cell embryos suggesting that this morphological criterion could be used for embryo aneuploidy screening [4,16,17].…”

Delayed blastulation, multinucleation, and expansion grade are independently associated with live-birth rates in frozen blastocyst transfer cycles

“…Often such embryos are deselected from fresh transfers, but they may be cryopreserved for a subsequent frozen transfer (4,(13)(14)(15)(16). Trophectoderm biopsies with genetic analysis indicate that not all blastocysts derived from multinucleated embryos have an abnormal chromosome complement (14,17). Our study identified the blastocyst features independently predictive of successful pregnancy and live birth with vitrified-warmed blastocysts.…”

Multinucleation per se is not always sufficient as a marker of abnormality to decide against transferring human embryos

“…Multinucleation (MN) might decrease the rate of implantation of embryos after their transfer to the uterus, presumably from chromosomal aberrations and/or mosaicism (1)(2)(3)(4)(5)(6)(7)(8). On the other hand, it has been shown that healthy babies can be born from embryos with MN (9,10). Multinucleation might be a result as well as a cause of chromosomal aberrations such as chromosomal instability in Hela cells transfected with Chlamydia trachomatis (11).…”