Assessment of Risk Factors and Risk Stratification for Venous Thromboembolism (VTE) in Pregnancy: A Study Conducted in A Tertiary Level Hospital

Abstract

Background: Pregnancy itself is one of the most provoking factors for the development of venous thromboembolism (VTE) with an incidence of 5-12 per 10 000 pregnancies (from conception to delivery, i.e., 40 weeks) and 3-7 per 10 000 deliveries postpartum (6 weeks).1 Moreover, certain clinical conditions and individual patient profile make each pregnant women more susceptible to develop symptomatic VTE comprising deep vein thrombosis (DVT) and pulmonary embolism (PE). There is no denial of the fact that risk stratification based upon individual risk factors (both clinical and biochemical) during antenatal period will rationalize the implementation of precise antenatal care/ personalized prophylaxis tailored to each pregnant women, ultimately leading to safe and healthy maternal and perinatal outcome. Objective: The objective of this study is to apply the documented assessment scoring system according to the RCOG Guideline 37a mainly based on clinical risk factors to detect and stratify antenatal patient risk of VTE and institute appropriate preventive treatment/advice. Method: This is a prospective cross-sectional study involving 50 antenatal/pregnant women randomly selected over a period of 6 months undergoing antenatal care in Bangladesh Medical College. For the assessment of risk of VTE in these patients, RCOG guideline 37a risk assessment tool was used. (Appendix 1) A score ranging from 0 to 4 or more was objectively found among these patients. Based upon the score, each patient was categorized as high risk, intermediate risk, and lower risk. Then thromboprophylaxis with LMWH (Enoxaparin)/mobilization was advised for variable durations depending upon the timing of presentation and scores. The patients were reassessed after admission and post-delivery using the same tool for change in transient factors and advised according to the score. Implementation of this risk stratification tool resulted in improved patient care and counselling; the pregnancy outcome of each case was followed up. Results: Among the fifty antenatal patients, RCOG guideline 37a risk assessment tool revealed the following scores: one patient scored zero. Eighteen patients scored one. Sixteen patients scored two. Nine patients scored three. Six patients scored four. Those who scored 0 and 1 (19 patients) required no thromboprophylaxis. The sixteen patients with a score of two were advised for post-natal thromboprophylaxis with low molecular weight heparin/ Enoxaparin (LMWH) for 10 days. They were reassessed/ re-scored in the postnatal period for VTE risk and 5 of these patients down scored to one. Thereby they were judged as not to require post-natal thromboprophylaxis and were advised early mobilization and avoidance of dehydration. The remaining 11 patients with a score of two on postnatal review were put on LMWH (Enoxaparin) at a dose of 20 mg daily subcutaneous (s.c.) (<50 kg), 40 mg daily (50-90 kg), 60 mg daily in 2 divided dose (91-130 kg) for 10 days. Conclusion: Pulmonary embolism is a dreaded consequence of VTE in pregnancy and post-partum, resulting in sudden severe maternal morbidity and mortality. Individualized scoring of the risk of VTE or early detection of DVT (deep venous thrombosis) with subsequent treatment /prophylaxis can reduce /eliminate the risk of maternal death related to VTE. Implementation of risk stratification for VTE of antenatal patients has resulted in a change of practice emphasising preventive measures such as mobilisation and anticoagulation according to the objective scoring system. It is clear that the antepartum and postpartum periods have different magnitudes of risk and distinct risk factors for VTE and therefore must be considered separately. As a continuum of care, carefully reviewed post-partum risk factors has also been proposed by the RCOG in the GTG 37a guideline. Low-molecular-weight heparin is safe in pregnancy and post-partum in prophylactic and therapeutic doses and does not require coagulation monitoring by haematological studies. LMW heparin provides advantages over heparin in that it has better bioavailability and longer half-life, simplified dosing, predictable anticoagulant response, lower risk of Heparin induced thrombocytopenia (HIT), and lower risk of osteoporosis. However, if monitoring is necessary particularly in case of ?Class II Obesity, renal insufficiency and presence of mechanical heart valves, anti–factor Xa levels must be measured because LMWH preparations have little effect on activated partial Thromboplastin Time (aPTT).