12-phase flow (12)

1. 1FRAME
   VTE in pregnancy and postpartum — pregnant and postpartum patients have 4-5x increased VTE risk vs non-pregnant; ~ 80% events are venous; prevalence 0.5-2.0 per 1000 pregnant women per ACOG PB 196 (PMID 29939938). VTE accounts for ~ 9.3% of US maternal deaths. Anticoagulation choice is tailored to pregnancy because warfarin is teratogenic (PregCat X in pregnancy; warfarin embryopathy 6-12 wk; fetal hemorrhage later) and DOACs lack pregnancy/lactation evidence and are contraindicated. LMWH (enoxaparin) is the backbone per ASH 2018 (Bates PMID 30482767) STRONG recommendation over UFH for acute VTE; UFH only near delivery and in eGFR < 30. Diagnosis uses pregnancy-adapted YEARS algorithm for PE (van der Pol 2019 PMID 30893534).
   inputs: gestational_age_or_postpartum_interval
   advance: GA / postpartum interval documented; VTE pretest probability and anticoagulation framework set
2. 2ENTRY
   Recognise VTE via unilateral leg swelling/pain (DVT), pleuritic chest pain / dyspnea / hemoptysis (PE), unexplained sinus tachycardia or hypoxemia, sudden cardiopulmonary collapse (massive PE — AFE differential important), or new bilateral leg swelling + abdominal pain (iliofemoral DVT, more common in pregnancy due to uterine compression of left iliac vein). Differential: cellulitis, superficial venous thrombosis, ruptured Baker cyst, lymphedema (for DVT); pneumonia, cardiomyopathy, AFE, anxiety/hyperventilation, costochondritis (for PE).
   inputs: gestational_age_or_postpartum_interval
   advance: VTE suspected; diagnostic pathway initiated (compression US for DVT; YEARS algorithm for PE)
3. 3CONTEXT
   Capture prior VTE (personal + family history) and type (unprovoked / hormonally associated / provoked); known thrombophilia (inherited: FVL, prothrombin gene, antithrombin, protein C/S; acquired: APS); maternal weight/BMI for weight-based LMWH dosing; mode of delivery if postpartum (cesarean doubles risk); comorbid risk factors (BMI > 30, smoking, immobility, HG with dehydration, pre-eclampsia, multifetal gestation); current anticoagulation status (transition DOAC/warfarin to LMWH if pregnant).
   inputs: prior_vte_personal_or_family, known_thrombophilia_diagnosis, maternal_weight_or_bmi, mode_of_delivery_cesarean_vs_vaginal, comorbid_obesity_smoking_immobility_HG_preeclampsia, current_anticoagulation_status_and_class
   advance: Risk-factor + contraindication context + anticoagulation status captured
4. 4RED_FLAGS
   Hemodynamic instability with massive PE (SBP < 90 / MAP < 65 / shock / arrest) → consider thrombolysis with alteplase (life-threatening indication only); respiratory failure → intubation + ICU + ECMO consideration; sudden severe PE-pattern + intrapartum/immediate postpartum → AFE differential (ob.amniotic-fluid-embolism.v1); HIT suspicion (platelet drop within 5-10 d of heparin exposure) → switch to non-heparin anticoagulant (argatroban, fondaparinux off-label in pregnancy).
   inputs: maternal_bp, maternal_hr, maternal_spo2
   advance: Red-flag pathway activated: thrombolysis decision, ICU/ECMO consideration, AFE ddx routed, HIT screened
5. 5INITIAL_WORKUP
   DVT workup: compression ultrasound of leg (proximal + distal veins); MRV if iliofemoral DVT suspected and US negative/limited. PE workup: pregnancy-adapted YEARS algorithm (van der Pol 2019 NEJM PMID 30893534) — if zero YEARS items + D-dimer < 1000 ng/mL OR ≥ 1 YEARS item + D-dimer < 500 ng/mL, PE excluded without imaging (safe in ~ 39% of pregnant patients); otherwise CTPA preferred (low fetal radiation; minimal maternal breast radiation if shielding used) or V/Q scan (lower breast radiation but slightly higher fetal radiation, often inadequate if CXR abnormal). Baseline CBC + creatinine + coag + troponin/BNP if PE confirmed. ECG. Bedside echo for RV strain in confirmed PE.
   inputs: compression_ultrasound_lower_extremity, maternal_cbc_with_platelets, maternal_creatinine_egfr, maternal_coagulation_pt_aptt, ecg_baseline
   actions: panel.cbc, panel.renal, panel.coag
   advance: DVT/PE confirmed or excluded; severity stratified; baseline labs for anticoagulation
6. 6BRANCHING_WORKUP
   If PE confirmed → echo for RV strain (severity stratification); troponin + BNP (submassive risk markers); right heart catheterization rarely if pulmonary HTN ambiguous. If iliofemoral DVT → MRV; consider catheter-directed thrombolysis for limb-threatening or massive iliofemoral DVT (rare in pregnancy; case-by-case with hematology + IR). HIT antibody panel if HIT suspected. Thrombophilia workup deferred until off anticoagulation (acute thrombus + heparin confound results).
   inputs: maternal_troponin_and_bnp, bedside_transthoracic_echo_for_rv_strain
   advance: Severity stratified; HIT screened; thrombophilia workup deferred
7. 7DIFFERENTIAL
   DVT differential: cellulitis (warmth, redness, no Homan sign), superficial venous thrombosis (palpable cord), ruptured Baker cyst (popliteal), lymphedema (pitting, gradual), trauma/hematoma, post-thrombotic syndrome (if prior VTE). PE differential: pneumonia (fever, productive cough, focal infiltrate), peripartum cardiomyopathy (cardiomegaly, BNP markedly elevated, LV dysfunction), amniotic fluid embolism (sudden intrapartum/immediate postpartum collapse + DIC), acute coronary syndrome (chest pain, ECG, troponin), pneumothorax (decreased breath sounds, CXR), anxiety/hyperventilation (clinical exclusion), costochondritis (reproducible CW tenderness), aortic dissection (rare in young pregnant patient).
   advance: Differential narrowed; alternative dx routed if present
8. 8RISK_STRATIFICATION
   PE severity: MASSIVE (SBP < 90 sustained > 15 min, requiring vasopressors, cardiac arrest); SUBMASSIVE (normotensive but RV strain on echo + elevated troponin/BNP); LOW-RISK (normotensive, no RV strain, normal biomarkers). Massive PE in pregnancy → thrombolysis with alteplase is reasonable for life-threatening indication; submassive PE → therapeutic LMWH + close monitoring (catheter-directed thrombolysis selectively per IR + hematology); low-risk PE → LMWH + outpatient management consideration per ASH 2018 (Bates PMID 30482767) conditional recommendation. sPESI useful for postpartum prognosis but not validated in pregnancy.
   inputs: maternal_bp, maternal_troponin_and_bnp, bedside_transthoracic_echo_for_rv_strain
   advance: Severity tier (massive / submassive / low-risk) assigned; thrombolysis vs anticoagulation alone decision made
9. 9TREATMENT
   ACUTE VTE: LMWH enoxaparin 1 mg/kg SC q12h (weight-based; therapeutic) — ASH 2018 STRONG recommendation over UFH (Bates PMID 30482767). UFH if eGFR < 30 mL/min/1.73 m² OR near delivery (24 h before scheduled induction/elective cesarean for therapeutic dose; 12 h for prophylactic). Anti-Xa monitoring NOT routinely needed (ASH 2018 conditional against); reserve for extremes of body weight, renal impairment, or recurrent VTE on therapy. Restart 4-6 h post vaginal delivery / 6-12 h post cesarean depending on hemostasis. WARFARIN: POSTPARTUM ONLY (CONTRAINDICATED in pregnancy due to embryopathy 6-12 wk + fetal hemorrhage; LactMed compatible postpartum since does not transfer to breast milk in significant amounts). DOACs: CONTRAINDICATED in pregnancy AND lactation (apixaban, rivaroxaban, dabigatran, edoxaban — ASH 2018 no recommendation due to limited data + theoretical small-molecule milk transfer). MASSIVE PE WITH HEMODYNAMIC INSTABILITY: alteplase 100 mg IV over 2 h (or 50 mg if cardiac arrest) — life-threatening indication; relative pregnancy contraindication outweighed by survival benefit. IVC FILTER: only for absolute anticoagulation contraindication (active major hemorrhage); retrievable filter preferred. ANTICOAGULATION DURATION: 3 mo TOTAL OR 6 wk postpartum, whichever is longer (ACOG PB 196 + ASH 2018).
   inputs: gestational_age_or_postpartum_interval, maternal_weight_or_bmi, maternal_creatinine_egfr
   advance: Anticoagulation initiated at correct dose; transition plan to delivery documented; thrombolysis decision made if massive PE
10. 10DISPOSITION
    OUTPATIENT initiation for low-risk acute DVT or stable PE per ASH 2018 conditional recommendation (Bates PMID 30482767) when reliable follow-up + hemodynamic stability + no high-risk features. ED for new VTE presentation, diagnostic workup, anticoagulation initiation. INPATIENT for massive PE, ICU-level care, thrombolysis, postpartum hemorrhage on anticoagulation, intrapartum management of patient on LMWH/UFH. ICU for massive PE with shock, post-thrombolysis monitoring, ECMO consideration.
    inputs: maternal_bp
    advance: Level of care set; outpatient follow-up scheduled if discharged; admission for high-risk
11. 11MONITORING
    CBC + creatinine baseline + monthly (LMWH adjustment for renal/weight changes); anti-Xa NOT routine; check if extremes of weight (< 50 kg, > 100 kg), renal impairment (CrCl < 30), recurrent VTE on therapy — target 0.6-1.0 IU/mL on therapeutic enoxaparin q12h. Platelet count d 5-10 of heparin therapy to screen HIT. Clinical reassessment q1-2 wk first month then monthly. Transition planning at 34-36 wk: switch therapeutic enoxaparin → UFH 24 h before induction/elective cesarean; prophylactic LMWH 12 h before. Resume 4-6 h post vaginal delivery / 6-12 h post cesarean.
    inputs: maternal_cbc_with_platelets, maternal_creatinine_egfr
    actions: panel.cbc, panel.renal
    advance: Stable on therapy; transition to delivery planned; HIT screened; postpartum plan documented
12. 12FOLLOWUP
    Continue anticoagulation 3 mo total OR 6 wk postpartum (whichever is longer) per ACOG PB 196 (PMID 29939938) + ASH 2018 (Bates PMID 30482767). Postpartum transition: warfarin acceptable (LactMed compatible — no milk transfer) OR continue LMWH/fondaparinux throughout breastfeeding; AVOID DOACs during breastfeeding per ASH 2018. Thrombophilia workup AFTER anticoagulation completed (acute thrombus + heparin confound results). Subsequent-pregnancy counseling: prophylactic LMWH throughout pregnancy + 6 wk postpartum if VTE in prior pregnancy or known thrombophilia (ACOG PB 196 risk-stratified). Contraception counseling: AVOID combined OCs (estrogen) given VTE history; progestin-only methods or non-hormonal preferred. Lifestyle: weight optimization, smoking cessation, mobility.
    advance: Anticoagulation duration completed; thrombophilia workup if indicated; subsequent-pregnancy plan + contraception counseling delivered