Effect of Low Molecular Heparin on Pregnancy Outcome With Protein S Deficiency

Inclusion Criteria: 1. Plasma activity levels of PS when not pregnant are below the lower limits of the adult reference values (generally about 60-70% for PS) without the use of warfarin. Or, free protein S antigen levels in the second and third trimesters are less than 30% and less than 24%, respectively 2. Pregnant women who delivered from Aug 1st, 2024 to Oct 15th, 2027 3. One or more family members exhibiting the same symptoms as the patient 4. Past history of early onset thrombosis (age 50 or below) 5. Repeated recurrence of thrombosis 6. Thromboses in unusual sites 7. New onset of thrombosis during current pregnancy or after delivery 8. Patients with diagnosis confirmed by gene analysis Inclusion criteria 1 and 2 must always be met regardless of items of 3-8. 9. Written informed consent Exclusion Criteria: 1. Thrombophilia other than Protein S deficiency 2. Antiphospholipid syndrome, systemic lupus erythematosus, platelet abnormalities, vascular disorders, blood flow obstruction, paroxysmal nocturnal hemoglobinuria, malignant tumor and other conditions that tend to cause thrombosis 3. Allergy/hypersensitivity to enoxaparin or aspirin 4. Heparin-associated thrombocytopenia or thrombocytopenia (platelet count\<75 × 10\^9/L) 5. Organ lesions at risk for bleeding such as acute stomach/bowel ulcers, cerebral hemorrhage, cerebral aneurysm 6. uncontrolled hypertension or Severe hypertension (Systolic Blood Pressure \>200mmhg and/or Diastolic Blood Pressure \>120mmHg) 7. Severe hepatic failure (INR \>1.8) 8. Serum creatinine greater than 80 umol/L (1.3mg/dl) and an abnormal 24 hour urine creatine clearance (\<30ml/min) 9. Abnormal uterine cavity on hysterosalpingogram/hysteroscopy