Post-partum haemorrhage (PPH) is excessive bleeding from the genital tract following childbirth and is one of the major causes of maternal morbidity and mortality. Traditionally, primary PPH is defined as blood loss of 500 mL or more within the first 24 hours after vaginal birth, while blood loss of 1,000 mL or more after birth is considered clinically significant, irrespective of the mode of delivery. PPH may occur after vaginal delivery as well as after caesarean section. It can develop suddenly and rapidly, therefore early recognition, prompt assessment and immediate management are essential in maternal health nursing. Causes The causes of PPH are commonly remembered by the four Ts: Tone, Trauma, Tissue and Thrombin. Tone: Uterine atony is the most common cause of PPH. After delivery, contraction of the uterine muscle compresses the blood vessels at the placental site and controls bleeding. If the uterus fails to contract effectively, excessive bleeding occurs. Risk factors for uterine atony include prolonged or very rapid labour, over-distended uterus due to multiple pregnancy or polyhydramnios, large baby, prolonged use of oxytocin, grand multiparity, retained placenta and uterine infection. Trauma: Trauma to the genital tract can cause significant bleeding even when the uterus is well contracted. It includes cervical, vaginal and perineal tears, episiotomy-related bleeding, uterine rupture and uterine inversion. Instrumental delivery and operative procedures increase the risk of genital tract trauma. Tissue: Retained placental tissue or membranes may prevent effective uterine contraction and lead to continued bleeding. Retained placenta may occur because of abnormal placental adherence or incomplete separation. Placenta accreta and related placental attachment disorders can produce severe haemorrhage. Thrombin: Coagulation disorders can cause or worsen PPH. They may be associated with conditions such as placental abruption, severe pre-eclampsia, amniotic fluid embolism, intrauterine fetal death or disseminated intravascular coagulation. Other contributing factors include anaemia, previous PPH, multiple gestation, macrosomia, prolonged labour, maternal exhaustion and infections. Classification PPH may be classified as primary and secondary. Primary PPH occurs within the first 24 hours following childbirth. It is usually associated with uterine atony, genital tract trauma, retained placental tissue or coagulation abnormalities. Secondary PPH occurs after the first 24 hours and may develop up to 12 weeks after childbirth. Common causes include retained products of conception, subinvolution of the uterus, infection and, less commonly, coagulation disorders. PPH can also be classified according to severity. Blood loss of 500–1,000 mL is considered significant, while loss exceeding 1,000 mL with signs of hypovolaemia represents severe PPH. The clinical condition of the mother is more important than estimation of blood loss alone because visual estimation may underestimate actual blood loss. Clinical Manifestations The main manifestation is excessive vaginal bleeding. The blood may be bright red and may contain clots. In uterine atony, the uterus is usually soft, enlarged and poorly contracted.