1. Department of Obstetrics, Yantaishan Hospittal, Yantai 264000, China
2. Outpatient Department, Qingdao Eighth People’s Hospital, Qingdao 266100, China
3. Traditional Chinese Medicine Department, The Affiliated Qingdao Central Hospital of Qingdao University, The Second Affiliated Hospital of Medical College of Qingdao University, Qingdao 266042, China
4. Department of Obstetrics, The Affiliated Qingdao Central Hospital of Qingdao University, The Second Affiliated Hospital of Medical College of Qingdao University, Qingdao 266042, China