1. Department of Obstetrics, The Affiliated Hospital of Qingdao University, Qingdao, China
2. Department of Biology, The First Senior High School of Chengwu, Heze, China
3. Department of Medical Specimen Collection, The Affiliated Hospital of Qingdao University, Qingdao, China
4. Prenatal Diagnosis Center, The Affiliated Hospital of Qingdao University, Qingdao, China
5. Department of Biology, The Medical College of Qingdao University, Qingdao, China