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Article History

Received: 25 July 2019

Accepted: 24 September 2019

First Online: 5 October 2019

Compliance with ethical standards

:

: The authors have nothing to disclose.

: All procedures performed in the present study were in accordance with the ethical standards of the institutional research committee of Tokyo Women’s Medical University School of Medicine (approval no. 3932) and with the tenets of the Declaration of Helsinki of 1964 and its later versions.

: As the present study was an observational and historical but not a prospective interventional study, the ethics committee waived the need for direct informed consent. Instead, we offered patients the opportunity to opt-out to participate (a passive informed consent).