Study design and study population
RECRUITMENT
This single-center RCT was conducted at the Assisted Reproduction Center, Northwest Women’s and Children’s Hospital, Xi’an, China. The study protocol was approved by the ethics committee of Northwest Women’s and Children’s Hospital (approval number: 2018027), and was registered as ChiCTR1800020342 at Participants’ enrollment was scheduled to be completed from January 10, 2019 to January 10, 2020. But the number of planned recruits was not reached by January 10, 2020. We had planned to apply for extending the trial to enroll enough patients, but our center suspended all new IVF treatments due to the COVID-19 pandemic in January 24, 2020. Hence, the trial recruitment was terminated on January 10, 2020.Women were eligible if they met the following inclusion criteria (