The uterine veins form the uterine venous plexus in the broad ligament alongside the uterine artery, draining the uterus into the internal iliac vein. The plexus is extensive and highly variable, with multiple connections to the ovarian venous plexus, the vaginal plexus, and the vesical plexus. During pregnancy, the uterine veins enlarge dramatically to accommodate the increased uterine blood flow (reaching 500-750 mL/min at term).
The uterine venous plexus is the primary source of haemorrhage in obstetric emergencies: uterine atony, placenta praevia, placenta accreta, and uterine rupture all involve the uterine venous plexus. Bilateral uterine artery ligation (O'Leary sutures) reduces uterine blood flow from the arterial side, but the venous plexus continues bleeding from collateral flow. B-Lynch compression sutures mechanically compress the venous plexus. Internal iliac artery ligation reduces uterine perfusion pressure, reducing venous plexus haemorrhage. Uterine vein thrombosis (ovarian vein thrombosis extending to uterine veins) is a rare post-partum complication.
Placenta accreta invades the myometrium and uterine venous plexus, producing massive haemorrhage when the placenta is separated; planned caesarean hysterectomy without attempting placental separation is the standard management for accreta spectrum disorders identified pre-operatively, with interventional radiology balloon occlusion of the internal iliac arteries reducing intraoperative venous plexus haemorrhage.
