Effect of Day 3 cell number on the live birth rate of vitrified-warmed Day 5 single blastocyst transfer in young women

Abstract

Abstract Background Previous studies have reported inconsistent results regarding blastocyst selection with a high day 3 (D3) cell number and the eventual pregnancy outcomes. Thus, in this study, the relationship between the D3 cell number and clinical outcomes of day 5 single blastocyst transfer (SBT) in vitrified-warmed transfer cycles was investigated. Methods Our retrospective study included 1144 day 5 SBT in vitrified-warmed cycles between February 2016 and February 2021. All cycles were the first vitrified-warmed cycles, and the female patients were less than 35 years of age. Based on the D3 cell number, the cycles were divided into four groups, as follows: group A (3–7 cells, n = 130); group B (8–9 cells, n = 621); group C (10–12 cells, n = 328); and group D (13–16 cells, n = 65). The differences in the live birth rate (LBR), clinical pregnancy rate, and miscarriage rate were examined among the four groups. Results The LBR and clinical pregnancy rate increased with the D3 cell number (P 9 cells) was associated with a high LBR in the vitrified-warmed day 5 SBT cycles of patients 9 cells on D3 can be preferentially selected for transplantation.

Keywords

• Day 3 cell number
• Single blastocyst transfer
• Vitrified-warmed cycles
• Live birth rate