What is VTE and why is pregnancy a risk factor?+
VTE (venous thromboembolism) includes deep vein thrombosis (DVT, a clot in a deep vein, usually the leg) and pulmonary embolism (PE, a clot in the lung). Pregnancy increases VTE risk 4 to 5-fold due to three physiological changes: a hypercoagulable blood state (elevated clotting factors, reduced natural anticoagulants), venous stasis from uterine compression, and vascular wall changes from hormones. VTE is a leading cause of direct maternal mortality in high-income countries. Risk peaks in the first 2 weeks after birth.
What RCOG VTE score is considered high risk during pregnancy?+
A score of 4 or above during the antenatal period is high risk per RCOG Green-top Guideline No. 37a. Women with this score should be considered for low-molecular-weight heparin (LMWH) thromboprophylaxis from the first trimester throughout pregnancy, and for at least 6 weeks after delivery. A score of 2 to 3 is moderate risk, triggering prophylaxis from 28 weeks. A score of 0 to 1 is lower risk and requires only mobilization and hydration.
What is LMWH thromboprophylaxis in pregnancy?+
LMWH (low-molecular-weight heparin) is an injectable anticoagulant given once or twice daily under the skin. Common examples include enoxaparin (Clexane) and dalteparin (Fragmin). LMWH does not cross the placenta and is safe for the fetus. It prevents VTE by reducing excessive clotting. Dosing is weight-adjusted. Women on LMWH should hold their dose when labor begins and resume 4 to 6 hours after vaginal delivery or 6 to 12 hours after cesarean, once hemostasis is confirmed.
Which thrombophilias are high risk versus low risk in the RCOG score?+
High-risk thrombophilias (3 points) include antiphospholipid syndrome (APS), homozygous Factor V Leiden mutation, combined thrombophilias (two or more defects), and protein C or protein S deficiency. Low-risk thrombophilias (1 point) include heterozygous Factor V Leiden, heterozygous prothrombin gene mutation (G20210A), and antithrombin deficiency. The specific subtype and prior VTE history modify management; consult a hematologist for thrombophilia-related decisions.
Does a VTE score of 0 to 1 mean I am safe from blood clots in pregnancy?+
A score of 0 to 1 indicates lower background risk and does not require pharmacological prophylaxis in most guidelines. However, lower-risk women should still maintain hydration, avoid prolonged immobility, and promptly report VTE symptoms: unilateral leg swelling, warmth, or redness (DVT); sudden breathlessness, pleuritic chest pain, or rapid heart rate (PE). If a new risk factor develops (hospital admission, infection, bed rest), the score should be recalculated immediately.
Why does emergency cesarean add more points than elective cesarean?+
Emergency cesarean (2 points) carries a higher VTE risk than elective cesarean (1 point) because it is typically performed under greater urgency, with less optimal preparation, often after prolonged labor (which itself increases stasis), and with higher rates of associated complications like infection and hemorrhage. Elective cesarean is planned and performed in a controlled setting, with thromboprophylaxis routinely given. Both are higher risk than vaginal delivery (0 points).
How long should postnatal LMWH continue after delivery?+
Duration depends on the postnatal risk score. A score of 2 to 3 warrants 10 days of LMWH. A score of 4 or above warrants at least 6 weeks. Women with ongoing risk factors (active cancer, prior VTE, high-risk thrombophilia) may need extended prophylaxis. If postpartum hemorrhage occurred, LMWH may be delayed until bleeding is controlled and the clinical team confirms it is safe to restart anticoagulation.
What are the symptoms of DVT and PE to watch for in pregnancy?+
DVT symptoms include unilateral leg swelling (especially left leg), calf pain or tenderness, warmth, and redness. Symptoms in the thigh or groin may indicate a proximal DVT. PE symptoms include sudden breathlessness, sharp chest pain that worsens with breathing (pleuritic), coughing up blood, rapid heart rate, dizziness, or collapse. These symptoms overlap with normal pregnancy complaints and should be urgently evaluated with imaging, not managed conservatively.
Can I breastfeed while on LMWH for postnatal VTE prophylaxis?+
Yes. LMWH does not pass into breast milk in clinically meaningful quantities and is safe during breastfeeding. Standard postnatal LMWH doses pose no risk to the newborn through breast milk. Women receiving postnatal thromboprophylaxis can and should continue breastfeeding normally. Warfarin, which transitions some women from LMWH post-delivery, is also generally considered compatible with breastfeeding, though LMWH is preferred for most short-duration prophylaxis scenarios.
When should VTE risk be reassessed during pregnancy?+
RCOG recommends reassessing VTE risk at booking (first prenatal visit), at 28 weeks, and whenever a new acute risk factor develops (hospital admission, infection, dehydration, immobility, new diagnosis). The score is a snapshot, not a static assessment. A woman who starts at score 1 (lower risk) but develops a urinary tract infection requiring admission, bed rest, and IV fluids may rapidly accumulate 3 additional points (infection 1 pt, immobility 1 pt, IV fluids indicating dehydration) and cross the moderate-risk threshold.
How is this VTE risk score different from the Wells DVT score?+
They serve opposite clinical purposes. The Wells DVT score is a diagnostic tool: it estimates pre-test probability of confirmed DVT in a symptomatic patient, guiding whether to order a compression ultrasound or D-dimer. This RCOG VTE score is a prophylactic screening tool: it identifies asymptomatic women at risk so they receive preventive treatment before any clot develops. Never use the Wells score for prophylaxis decisions or this RCOG score for diagnostic workup.