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Obstruction of major pelvic or thigh veins raises pressure in the channels draining the limb; fluid then accumulates in the tissues as oedema. Severe outflow obstruction can also impede lymphatic drainage. The pale, tense appearance accounts for “alba”. It differs from phlegmasia cerulea dolens, in which more complete obstruction, including collateral channels, produces a congested blue limb and can threaten arterial perfusion. A historical case description cannot automatically be assigned one modern diagnosis solely from its name.

The central causal mechanisms are slowed venous flow, injury to the vessel wall and increased tendency of the blood to clot. Pregnancy promotes hypercoagulability and pelvic venous compression; childbirth can add tissue injury, immobility and infection. Prior venous thrombosis, thrombophilia, prolonged immobility, operative delivery and severe systemic illness further increase risk. It is not confined to the puerperium or even to women. The serious consequences are extension of the thrombus, detachment into the pulmonary arteries as a pulmonary embolism, and chronic obstruction or valvular damage producing post-thrombotic syndrome.^[ref]

An historically informed explanation should recognise that nineteenth-century arguments concerned the relative importance of venous obstruction, phlebitis, lymphatic disease and puerperal illness. Rest, support and elevation of the limb, pain relief and local soothing applications belonged to the period's conservative repertoire. These could ease symptoms but did not provide effective anticoagulation. Neither the “milk leg” name nor the observation of puerperal infection establishes that every case is caused by milk displacement or by infected clot. The thrombotic and infective questions must be distinguished.

Current management begins with clinical assessment and compression ultrasonography. A normally patent vein collapses under appropriate transducer pressure; a thrombosed segment often fails to compress. Doppler ultrasonography adds information about flow, and suspected pelvic disease may require further imaging. A negative initial study does not close a strongly suspicious case; repeat or additional imaging may be needed. Fever and systemic illness prompt assessment for infection, while breathlessness, chest pain or collapse require urgent assessment for pulmonary embolism.^[ref]

Unless contraindicated, therapeutic low-molecular-weight heparin is the usual treatment during pregnancy. It limits further clot formation while the body's own processes deal with the existing thrombus; it is not an instant mechanical solvent. Management also provides analgesia, elevation and appropriate mobilisation once stable, with fitted compression for symptoms when suitable. Prolonged compulsory bed rest is not a general modern remedy. A threatened limb or suspected massive pulmonary embolism needs immediate specialist escalation; routine thrombolysis for every swollen leg would expose patients to unjustified haemorrhage.

For confirmed pregnancy-associated venous thromboembolism, treatment usually continues through the rest of pregnancy and for at least six weeks after birth, with at least three months' treatment in total; the delivery plan must account for bleeding and anaesthesia. Antibiotics address a demonstrated or strongly suspected infective complication, not uncomplicated venous thrombosis itself.^[ref]

A historical clinical term for a pale, painful, swollen limb, especially after childbirth, associated with extensive deep vein thrombosis. It is distinct from blue, severely congested phlegmasia cerulea dolens.