Why does postpartum haemorrhage cause heavy bleeding after birth?

After the placenta separates, the uterus normally contracts and compresses the blood vessels where it was attached. If the uterus stays soft, those vessels may keep bleeding. Other causes include placental tissue left in the uterus, a tear in the vagina or cervix, or a problem with blood clotting. Heavy bleeding can happen soon after birth or later during recovery. It may be accompanied by large clots, dizziness, weakness, a fast heartbeat, pale or clammy skin, breathlessness or fainting.

Heavy bleeding after birth needs immediate assessment. Tell the midwife, nurse or doctor at once if you are in a maternity unit. If you are at home, call local emergency services and do not drive yourself if you feel faint or weak. Lie down while waiting, keep someone with you, and use a pad so the amount and pattern of bleeding can be described. Do not wait for an appointment or try to manage rapidly increasing bleeding alone.

Call emergency services immediately for bleeding that is suddenly heavy or increasing, repeated large clots, faintness, severe weakness, racing heartbeat, confusion, breathlessness or severe abdominal pain. These signs can indicate significant blood loss and require rapid treatment. Even without these symptoms, contact your maternity team urgently if bleeding seems heavier than expected or becomes bright red again after it had been settling.

What is the likely source of the bleeding? How will you check whether the uterus is contracting and whether placental tissue or a tear is present? What treatment and monitoring do I need now, and which warning signs should prompt an immediate return?