1. Obstetrical Department, Affiliated Hospital of Qingdao University, Qingdao, Shandong, China;
2. Clinical Laboratory, Affiliated Hospital of Qingdao University, Qingdao, Shandong, China;
3. Transfusion Department, Lanzhou general hospital of Lanzhou Command, Lanzhou, Gansu, China;
4. Department of Nephrology, Affiliated Hospital of Qingdao University, Qingdao, Shandong, China;
5. Prenatal Diagnosis Center, Affiliated Hospital of Qingdao University, Qingdao, Shandong, China;
6. Clinical Laboratory, Municipal Hospital of Qingdao, Qingdao, Shandong, China