Postpartum Haemorrhage
Excessive bleeding after birth, most often because the emptied uterus fails to contract and clamp its own spiral arteries, managed by a mechanistically ordered sequence of uterotonics and haemostatic measures.
First principles
The pregnant uterus receives an enormous blood flow that must be switched off instantly at delivery
At term the uterus receives roughly 500–800 mL of blood per minute through dilated spiral arteries feeding the placental bed. There is no anatomical sphincter on these vessels. The only mechanism that stops them bleeding after the placenta separates is mechanical: the interlacing myometrial fibres contract and physically strangle the vessels running between them, the 'living ligatures'. Any failure of that contraction opens a torrential haemorrhage from a raw placental bed.
Educational content pending clinical review. Not medical advice.