Selection of best blastocyst is crucial in single blastocyst transfer cycles, which is based on blastocyst morphological parameters such as inner cell mass (ICM), trophectoderm (TE) and its inner diameter. We aimed to study relation between morphological parameter and sex ratio after single vitrified-warmed blastocyst transfer (SVBT). Current study based on data of single-center and performed by retrospective analysis of 1563 SVBT (911 patients) with minimal stimulation on 5th and 6th days. TE morphology, female age and blastocyst day are highly correlated with clinical pregnancy rate (CPR) and live birth rate (LBR). Also, A grade ICM significantly correlated with CPR than C grade. Additionally, probability of being male gender is 2.8 times higher in singleton live birth with A grade trophectoderm than C grade. Neither ICM morphology, LBR nor sex ratio were not related to trophoectoderm grade. Higher grade TE, younger the age of patient and selection of the day 5 blastocyst showed higher frequency of CPR and LBR. Therefore, consideration of these parameters is a better method to select the best embryo. On the other hand, the selection for transfer blastocyst based on quality and morphological parameters may inadvertently push the secondary sex ratio (SSR) in favor of female births.
Keywords: Blastocyst; Live birth; Morphological grade; Secondary sex ratio; Trophectoderm.
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