1. Department of Obstetrics and Gynaecology, Shandong Provincial Hospital Shandong University Jinan China
2. Maternal and Child Health Care Hospital of Shandong Province Jinan China
3. The Laboratory of Placenta‐Related Diseases Key Laboratory of Birth Regulation and Control Technology of National Health and Family Planning Commission of China Jinan China
4. Central Laboratory Shandong Provincial Hospital Affiliated to Shandong First Medical University Jinan China