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

TLDR

In human IVF, blastocyst selection traditionally relies on three morphological scores—blastocoele expansion, trophectoderm (TE) quality, and inner cell mass (ICM) grade—yet the independent predictive value of each for pregnancy outcomes remains uncertain. This retrospective study evaluated 1,117 fresh day‑5 single blastocyst transfers, correlating each morphological parameter with live‑birth outcomes. After adjusting for confounders, only TE grade independently predicted live birth, demonstrating that TE quality is a stronger predictor than ICM for successful implantation and hatching.

Abstract

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.