affiliation not provided to SSRN, Seoul National University - Department of Obstetrics and Gynecology, Seoul National University - Seoul National University Bundang Hospital, Seoul National University - Seoul National University Hospital, Seoul National University - Seoul National University Hospital, Seoul National University - Seoul National University Bundang Hospital, Seoul National University, Seoul National University - Seoul National University Bundang Hospital, Seoul National University - Seoul National University Bundang Hospital, Seoul National University - Seoul National University Hospital, Seoul National University - Department of Obstetrics and Gynecology, Seoul National University - College of Medicine and Seoul National University - Department of Obstetrics and Gynecology