Postpartum Haemorrhage
Postpartum haemorrhage is bleeding after birth that outruns the myometrial contraction meant to close the placental bed, usually from atony, retained tissue, trauma or failed clotting.
Definition
Primary postpartum haemorrhage (PPH) is the loss of 500 mL or more of blood from the genital tract within 24 hours of birth. It is minor at 500 to 1000 mL and major above 1000 mL. The Royal College of Obstetricians and Gynaecologists (RCOG) divides major into moderate, 1000 to 2000 mL, and severe, over 2000 mL. Secondary PPH is abnormal or heavy bleeding between 24 hours and 12 weeks after birth. These are postpartum figures: antepartum haemorrhage uses different volumes for the same words.
First principles
Muscle, not clot, seals the placental bed
After the placenta separates, its bed is a raw sinus fed by wide spiral arteries. Only contraction of the surrounding myometrium closes them, because platelets and fibrin cannot bridge vessels that size. The first treatments are therefore mechanical and pharmacological contraction, not clotting factors. A firm uterus that is still bleeding points away from atony.
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