Quantitative and qualitative trophectoderm grading allows for prediction of live birth and gender

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Abstract

<div class="section"> <a class="named-anchor" id="d8792483e175">  </a> <h5 class="section-title" id="d8792483e176">Purpose</h5> <p id="d8792483e178">Prolonged in vitro culture is thought to affect pre- and postnatal development of the embryo. This prospective study was set up to determine whether quality/size of inner cell mass (ICM) (from which the fetus ultimately develops) and trophectoderm (TE) (from which the placenta ultimately develops) is reflected in birth and placental weight, healthy live-birth rate, and gender after fresh and frozen single blastocyst transfer. </p> </div><div class="section"> <a class="named-anchor" id="d8792483e180">  </a> <h5 class="section-title" id="d8792483e181">Methods</h5> <p id="d8792483e183">In 225 patients, qualitative scoring of blastocysts was done according to the criteria expansion, ICM, and TE appearance. In parallel, all three parameters were quantified semi-automatically. </p> </div><div class="section"> <a class="named-anchor" id="d8792483e185">  </a> <h5 class="section-title" id="d8792483e186">Results</h5> <p id="d8792483e188">TE quality and cell number were the only parameters that predicted treatment outcome. In detail, pregnancies that continued on to a live birth could be distinguished from those pregnancies that aborted on the basis of TE grade and cell number. Male blastocysts had a 2.53 higher chance of showing TE of quality A compared to female ones. There was no correlation between the appearance of both cell lineages and birth or placental weight, respectively. </p> </div><div class="section"> <a class="named-anchor" id="d8792483e190">  </a> <h5 class="section-title" id="d8792483e191">Conclusions</h5> <p id="d8792483e193">The presented correlation of TE with outcome indicates that TE scoring could replace ICM scoring in terms of priority. This would automatically require a rethinking process in terms of blastocyst selection and cryopreservation strategy. </p> </div>

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Sex determines the expression level of one third of the actively expressed genes in bovine blastocysts.

P. Bermejo-Álvarez, D Rizos, D. Rath … (2010)

Although genetically identical for autosomal Chrs (Chr), male and female preimplantation embryos could display sex-specific transcriptional regulation. To illustrate sex-specific differences at the mRNA level, we compared gene-expression patterns between male and female blastocysts by DNA microarray comparison of nine groups of 60 bovine in vitro-produced blastocysts of each sex. Almost one-third of the transcripts detected showed sexual dimorphism (2,921 transcripts; false-discovery rate, P < 0.05), suggesting that in the absence of hormonal influences, the sex Chrs impose an extensive transcriptional regulation upon autosomal genes. Six genes were analyzed by qPCR in in vivo-derived embryos, which displayed similar sexual dimorphism. Ontology analysis suggested a higher global transcriptional level in females and a more active protein metabolism in males. A gene homolog to an X-linked gene involved in network interactions during spliceosome assembly was found in the Y-Chr. Most of the X-linked-expressed transcripts (88.5%) were up-regulated in females, but most of them (70%) exhibited fold-changes lower than 1.6, suggesting that X-Chr inactivation is partially achieved at the blastocyst stage. Almost half of the transcripts up-regulated in female embryos exhibiting more than 1.6-fold change were present in the X-Chr and eight of them were selected to determine a putative paternal imprinting by gene expression comparison with parthenogenetic embryos. Five (BEX, CAPN6, BEX2, SRPX2, and UBE2A) exhibited a higher expression in females than in parthenotes, suggesting that they are predominantly expressed by the paternal inherited X-Chr and that imprinting may increase the transcriptional skew caused by double X-Chr dosage.

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Effect of in vitro culture of human embryos on birthweight of newborns.

Edith Coonen, Josien G Derhaag, John Dumoulin … (2010)

In animal models, in vitro culture of preimplantation embryos has been shown to be a risk factor for abnormal fetal outcome, including high and low birthweight. In the human, mean birthweight of singletons after in vitro fertilization (IVF) is considerably lower than after natural conception, but it is not known whether culture conditions play a role in this. We compared pregnancy rates and perinatal outcomes from singleton pregnancies resulting from a total of 826 first IVF treatment cycles in which oocytes and embryos were randomly allocated to culture in either of two commercially available sequential media systems. When the 110 live born singletons in the Vitrolife group were compared with the 78 singletons in the Cook group, birthweight +/- SEM (3453 +/- 53 versus 3208 +/- 61 g, P = 0.003), and birthweight adjusted for gestational age and gender (mean z-score +/- SEM: 0.13 +/- 0.09 versus -0.31 +/- 0.10, P = 0.001) were both significantly higher in the Vitrolife group. When analyzed by multiple linear regression together with several other variables that could possibly affect birthweight as covariates, the type of culture medium was significantly (P = 0.01) associated with birthweight. In vitro culture of human embryos can affect birthweight of live born singletons.

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Trophectoderm morphology: an important parameter for predicting live birth after single blastocyst transfer.

A Ahlström, C. Westin, E Reismer … (2011)

In order to select the best blastocyst for transfer, in humans, three morphological parameters have routinely been used, i.e. degree of blastocoele expansion and appearance of both the trophectoderm (TE) and the inner cell mass (ICM). Although it has been shown that blastocysts with highest scores for all three parameters achieve highest implantation rates, their independent ability to predict pregnancy outcome remains unclear. This study is a retrospective analysis of 1117 fresh day 5 single blastocyst transfers and their live birth outcome related to each morphological parameter. All three parameters had a significant effect on live birth however, once adjusted for known significant confounders, it was shown that TE was the only statistically significant independent predictor of live birth outcome. This study has shown, for the first time, the predictive strength of TE grade over ICM for selecting the best blastocyst for embryo replacement. It may be that, even though ICM is important, a strong TE layer is essential at this stage of embryo development, allowing successful hatching and implantation.