Article History
Received: 2 December 2018
Revised: 28 January 2019
Accepted: 8 February 2019
First Online: 18 March 2019
Compliance with ethical standards
:
: The scientific guarantor of this publication is Baohua Li, who is from Department of Obstetrics, Women’s Hospital, Zhejiang University School of Medicine.
: The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.
: No complex statistical methods were necessary for this paper.
: Written informed consent was obtained from all subjects (patients) in this study.
: The present study was approved by the Institutional Review Board, Women’s Hospital, Zhejiang University School of Medicine.
: • retrospective• case-control study• performed at one institution