Obstetric haemorrhage is one of the leading causes of maternal mortality worldwide, and even in the more affluent societies, with ready access to resuscitation, uterotonics, blood transfusion and surgery, deaths still occur. Haemorrhage may be of rapid onset. It is important to recognize its severity promptly, institute effective therapy and keep ahead of the loss.

A vaginal examination should not be performed in the presence of antepartum vaginal bleeding without first excluding placenta praevia – ‘No PV until no PP’.

Vaginal bleeding associated with intrauterine pregnancy is divided into the following categories:

 threatened miscarriage – up to 24 weeks’ gestation

 antepartum haemorrhage – from 24 weeks’ gestation until the onset of labour

 intrapartum haemorrhage – from the onset of labour until the end of the second stage

 postpartum haemorrhage – from the third stage of labour until the end of the puerperium (6 weeks after delivery).

APH affects 3–5% of pregnancies. Placental abruption and placenta praevia are the most important causes of APH but are not the commonest. The majority of APH remains unexplained after clinical and ultrasound examination.

Antepartum haemorrhage is classified according to the source of the bleeding.

There may be bleeding from the vulva, vagina or cervix. Bleeding from the cervix is not uncommon in pregnancy and may follow sexual intercourse. A cervical ectropion or benign polyp is often found, and only very rarely is there cervical carcinoma. Later in pregnancy, the passing of a blood-stained ‘show’, mucus along with a small amount of blood, may simply herald the onset of labour as the cervix becomes effaced.

The risk of placenta praevia is of a sudden, unpredictable, major haemorrhage and some clinicians advocate hospital admission from 30–32 weeks onwards, so that facilities for resuscitation and delivery are immediately available. This can be socially difficult for the woman, particularly if she has children at home, and immobility in hospital may predispose to thromboembolic disease. Outpatient management is frequently undertaken, particularly for those who have had no bleeding (placenta praevia an incidental ultrasound finding) or just light bleeding, and who live close to the hospital with good social support and available transport. Elective delivery is usually planned for 38–39 weeks, but will be earlier if there is a major haemorrhage.

Caesarean section in the presence of placenta praevia should be directly supervised or performed by a senior obstetrician, since a large blood loss is frequently encountered due to the relatively poor capacity of the lower segment of the uterus to contract.

Anterior placenta praevia in the presence of a history of one or more caesarean sections predisposes the woman to placenta accreta, where the placenta invades the myometrium and cannot be readily separated from the uterus following delivery. Placenta accreta can be diagnosed with ultrasound antenatally and MRI is increasingly being used to improve accuracy of diagnosis. The presence of placenta accreta markedly increases the chance of severe haemorrhage and a multidisciplinary approach to delivery is recommended. Severe haemorrhage can require hysterectomy and women should be warned of this possibility prior to surgery.

History of a previous pregnancy affected by placental abruption and maternal cigarette smoking are among the risk factors for placental abruption, but the majority of placental abruptions occur by chance in women without identifiable risk factors.

Light bleeding from the edge of a normally situated placenta does not normally compromise the fetus and a brief episode of inpatient observation with subsequent surveillance of fetal growth with serial ultrasound fetal biometry is appropriate until delivery at term.

Major revealed haemorrhage is obvious, and urgent delivery is usually required. A major concealed abruption is inferred from the degree of pain, uterine tenderness and evidence of hypovolaemic shock; again, urgent delivery may be required. The decision between vaginal delivery and caesarean section is influenced by the degree of bleeding, maternal and fetal conditions.