Received: 8 December 2020
Accepted: 8 February 2021
First Online: 14 February 2021
Ethics approval and consent to participate
: This study was approved by the institutional review board of the National Defense Medical College, Tokorozawa, Japan. Records/information of all women in the study were completely anonymized and de-identified prior to analysis. The present study was exempt from collecting informed consent from all participants.
: Not applicable.
: The authors declare that they have no conflicts of interest.