Strategies in the transfer of varying grades of vitrified‐warmed blastocysts in women aged over 35 years: A propensity‐matched analysis

Aim For in vitro fertilization, the optimal number of blastocysts to transfer according to blastocyst grade has not been well established, especially with respect to vitrified‐warmed blastocyst transfer (VBT) in women aged over 35 years. This study aimed to compare the pregnancy and neonatal outcomes for three different VBT methods with variable numbers and qualities of blastocysts in women aged over 35 years. Methods All VBT cycles were categorized into three groups according to blastocyst grade: GG (two good‐quality blastocysts transferred), GP (one good‐quality blastocyst transferred with one of poor quality) and GS (one good‐quality blastocyst transferred). Blastocysts graded greater than or equal to 3BB were considered good quality. We conducted three 1:1 propensity score‐matched analyses (GG vs GS, GP vs GS and GG vs GP) to compare the clinical pregnancy rate (CPR), live birth rate (LBR), multiple pregnancy rate (MPR), preterm birth rate and low birthweight rate. Results Compared to GS, GG had higher CPR and LBR; however, MPR was also higher with GG. There were no significant differences, except implantation rate and MPR between GP and GS. Although implantation rate and CPR with GG were higher than those with GP, there were no significant differences in LBR and MPR. Conclusion To reduce high MPR after double blastocyst transfer methods, single good‐quality blastocyst transfers are recommended in the VBT of women aged over 35 years. Transferring a good blastocyst with a poor one should be avoided because it confers no advantage.