Clinical and neonatal outcomes of complete zona pellucida removal by laser-assisted hatching after single vitrified-warmed blastocyst transfer.

Laser-assisted hatching (LAH) is a widely used and unavoidable technique in assisted reproductive technology after frozen embryo transfer (FET). We aimed to investigate the safety and efficacy of completely ZP (zona pellucida) removed by an assisted laser group compared to an intact group after FET. This retrospective study involved 320 SVBT  single vitrified-warmed blastocyst transfers of 213 patients who underwent clomiphene citrate (CC) based minimal stimulation protocol. This study compared 160 SVBT with ZP that were completely removed using laser-assisted (laser beams of 10-15, a wavelength of 1.48 µm, and duration of 1.8-2.2 ms) to 160 cases of intact SVBT. Fisher's exact test, chi-squared test, and logistic regression are used for statistical analysis. The women's age, cause of infertility, BMI, transferred embryo day, insemination methods, and blastocyst grade were not significantly different between two groups. The implantation rate (66.2% vs. 51.2%, P < 0.01), the clinical pregnancy rate (CPR, 52.5% vs. 39.3%, P = 0.01), and the live birth rate (LBR, 43.7% vs. 29.3%, P < 0.01) were significantly higher in the completely ZP removed than the intact group. In logistic regression analysis, the laser-assisted hatching group showed about 2 times higher implantation rate and CPR and LBR than the control group. But miscarriage, gestational weeks, gender, birth weight, and twin births were insignificant between two groups. Our study suggests ZP free embryo transfer by assisted laser is more effective and safer than intact embryo transfer.

The trophectoderm could be better predictable parameter than inner cellular mass (ICM) for live birth rate and gender imbalance.

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.