title: Reply.
authors.affiliation: Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. Electronic address: junjimzhang@gmail.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
mesh_terms: D005260:Female; D006801:Humans; D007743:Labor, Obstetric / Q000502:physiology*; D015233:Models, Statistical; D007744:Obstetric Labor Complications; D011247:Pregnancy