Study design and patients
A retrospective study was performed at Xiamen University Affiliated
Chenggong Hospital. All the frozen-thawed blastocyst transfer (FBT)
cycles in the period between January 2012 and May 2019 were included.
Exclusion criteria were: (a) blastulation on day 7 (b) Blastocysts
derived from vitrified oocytes or vitrified cleavages. Cycles with
missing data and women lost to follow-up were secondarily excluded.
Patients undergoing single FBT with one GQE were defined as group G and
double FBT with one GQE plus one PQE were defined as group GP.
Institutional Review Board approval was obtained from the Ethics
Committee of the Medical College of Xiamen University.