Study design and patients
We performed a retrospective cohort study between June 2014 and December
2017 in the Center for Assisted Reproductive Technology of Northwest
Women’s and Children’s Hospital, Xi’an, China. All patients were
followed-up for one year. This study was approved by the ethics
committee of the hospital (number 2018002). As part of the clinical
process, all patients signed informed consent before the IVF/FET
procedure. Data was extracted from our electronic medical record system.
Women who underwent a first cycle of FET were eligible for the study.
Women with polycystic ovarian syndrome (PCOS) or other forms of
anovulation, and women in whom the thawed embryo did not survive in the
current FET cycle were excluded.