This study adopted a single-center, prospective, observational study design. A consecutive cohort of pregnant and postpartum women who met the inclusion criteria was recruited from Shanghai First People's Hospital between January 2026 and December 2028. Quantitative hemorrhage detection was performed using residual clinical blood samples, and the diagnostic value of this detection for hemolytic disease of the newborn (HDN) was analyzed.

Inclusion Criteria:

• Gestational Age: Singleton pregnant women with gestational age ≥ 20 weeks.
• Clinical High-Risk Factors (meeting at least one of the following criteria):
• Traumatic Factors: Abdominal trauma (e.g., traffic accident, fall), intrauterine fetal version, amniocentesis, chorionic villus sampling (CVS).
• Obstetric Complications: Placental abruption, placenta previa, preeclampsia, unexplained antenatal hemorrhage, post-interventional therapy for twin-twin transfusion syndrome (TTTS).
• Fetal Abnormalities: Fetal growth restriction (FGR), unexplained abnormal fetal heart rate monitoring, fetal hydrops, fetal anemia (elevated middle cerebral artery peak systolic velocity (MCA-PSV) detected by Doppler ultrasound).
• High-Risk Population with Maternal-Fetal Blood Group Incompatibility: Maternal-fetal ABO or Rh-negative blood group incompatibility; positive result of the first-trimester antenatal antibody screening in pregnant women.

Exclusion Criteria:

• Pregnant women complicated with severe hematological diseases (e.g., coagulation disorders, immune thrombocytopenic purpura) or autoimmune diseases.
• Newborns who withdrew treatment for non-study-related reasons or were lost to follow-up after birth, resulting in missing outcome data.
• Termination of pregnancy due to various causes.
• Failure to complete the analysis due to unqualified core clinical data (e.g., quantitative hemorrhage test results, bilirubin levels) or unsatisfactory specimens (hemolysis, insufficient volume).

1. Pregnant and postpartum women
2. Newborn