LDA and LMWH vs LDA Alone in High-risk Patients for Preeclampsia Prevention

Inclusion Criteria: * Singleton pregnancy * High risk for preeclampsia (risk \>1:150) based on FMF screening algorithm combining first-trimester ultrasound, biochemical markers, and medical history * Gestational age \<16 weeks at enrollment * Maternal age ≥18 years * Willing and able to provide written informed consent * Adequate ability for follow-up (direct telephone communication, accessible residence) Exclusion Criteria: * Multiple pregnancy * Current permanent aspirin use for other medical indications * Serious congenital fetal abnormality detected on ultrasound * Contraindication to aspirin or low molecular weight heparin including: known hypersensitivity, active peptic ulcer disease, bleeding disorders or coagulopathy, severe thrombocytopenia (platelet count \<100,000/μL), active or recent significant bleeding, history of heparin-induced thrombocytopenia * Pre-existing severe renal failure (creatinine clearance \<30 mL/min) * Unable to provide informed consent * Low probability of adequate follow-up (residence in remote areas without telephone access, accommodation in temporary structures)