Study design and patients
This retrospective cohort study includes 821 women with euploid embryo
who underwent frozen-thawed embryo transfer between January 2012 and
March 2020 in the Center for Assisted Reproductive Technology of
Northwest Women’s and Children’s Hospital, China. All the patients were
followed-up for one year after embryo transfer. This study was approved
by the ethics committee of the hospital (number 2019013). Because of the
retrospective character of the study, informed consent was waived.
Patient data were anonymized. Data was extracted from electronic medical
record system. Inclusion criteria were: first transfer cycle of a single
frozen-thawed, euploid blastocyst embryo after IVF with preimplantation
genetic testing for aneuploidies (PGT-A). Exclusion criteria were
multiple FET cycles. Patients were included a single time in the study.
BMI was calculated as weight divided by squared height. Women were
considered underweight if BMI was <18.5
kg/m2, normal weight if 18.5 kg/m2 ≤
BMI <25 kg/m2, overweight if 25
kg/m2 ≤ BMI <30 kg/m2, and
obese if BMI was ≥30 kg/m2 according to the most
recent BMI classification by the World Health Organization (WHO)
[8].