Poor-quality embryos compared with available embryos at cleavage stage have similar outcomes in vitrified-thawed single blastocyst transfer

Abstract Background It was known that in patients with good prognosis, day 5 good-quality blastocysts formed by available cleavage embryos (AEs) or poor-quality cleavage embryos (PQEs) did not affect clinical outcomes. However, the clinical outcomes of day 5/6 expanded blastocysts cultured in patients who faced with PQEs was unclear. Methods Retrospective cohort study was conducted among women aged ≤ 38 who underwent vitrified-warmed single blastocyst transfers (SBTs) which originated from AEs (n = 382), PQEs with AEs (n = 99), or only PQEs without AEs (n = 101). Results The PQEs compared to the AEs showed lower CPR (38.38% in PQEs with AEs; 36.63% in PQEs without AEs; versus 57.07% in AEs) and lower LBR (28.28%; 29.70%; versus 44.50%), but there was no statistical difference in CPR (adjusted OR 0.78, 95% CI 0.46–1.31; adjusted OR 0.82, 95% CI 0.47–1.42) and LBR (adjusted OR 0.91, 95% CI 0.53–1.59; adjusted OR 0.94, 95% CI 0.50–1.78) after controlling for confounding variables. Better outcomes were associated with thicker endometrial thickness (CPR: adjusted OR 1.18, 95% CI 1.05–1.33; LBR: adjusted OR: 1.16, 95% CI 1.03–1.30) and blastocyst expansion on day 5 (CPR: adjusted OR 2.52 95% CI 1.62–3.94; LBR: adjusted OR: 2.28, 95% CI 1.43–3.65). ICM score C (CPR: adjusted OR 0.08, 95% CI 0.01–0.67; LBR: adjusted OR: 0.10, 95% CI 0.01–0.76) were associated with worse outcomes. Conclusions Once the blastocyst was available, endometrial thickness, ICM grade, and the day of blastocyst expansion were the factors affecting the outcome, while the quality of cleavage embryos (PQEs or AEs) had no effect on subsequent clinical outcomes.