PPH · Postpartum Hemorrhage

The Deflating Balloon and the Faucet

Think of the uterus as a water balloon that has just squeezed out a sponge (the placenta). Normally, the balloon's rubber walls clamp down hard around the holes where the sponge was stuck, pinching the water pipes shut so only a trickle leaks out. This clamping is like uterine contraction—the muscle fibers act as living rubber that seals the spiral arteries. But in postpartum bleeding (hemorrhage), the balloon stays floppy and never squeezes, so the pipes stay wide open and water pours out like a faucet at full blast. Your body's early response is like turning up the water pump (heart) and narrowing the garden hose (blood vessels) to keep pressure in the main tank, but this trick only works while the faucet is still running—once you lose too much water, the whole system collapses and you go into shock. The only fix is to turn off the faucet (make the uterus contract) and pour water back in (transfuse blood) fast, or the balloon deflates completely.