Obstetric Haemorrhage

Local

There may be bleeding from the woman’s vulva, vagina or cervix. Bleeding from the cervix is not uncommon in pregnancy and may follow sexual intercourse (post-coital bleeding). A cervical ectropion or benign polyp is often found; rarely, a diagnosis of cervical carcinoma is made. The passing of a blood-stained ‘show’, mucus along with a small amount of blood, may herald the onset of labour as the cervix becomes effaced.

Placental

Placenta Praevia

The term ‘placenta praevia’ was previously defined using transabdominal ultrasound scan as a placenta that lies wholly or partly in the lower uterine segment. A grading system, I to IV, was employed based on the relationship and/or the distance between the lower placental edge and the cervical internal os ( Table 26.1 , Fig. 26.1 ). The site of the placenta may also be described by its position, for example, anterior, posterior or lateral. More recently, and with widespread use of transvaginal ultrasound scanning, an alternative definition and classification has been widely adopted; the placenta is described as low lying when the placental edge is less than 2 cm from the internal os and placenta praevia when the placenta lies directly over and covers the internal os. Placenta praevia is more common among women who have previously given birth by caesarean, but the majority of women with placenta praevia have no discernible risk factors.

Table 26.1

Traditional Classification of Placenta Praevia

Minor	I	Encroaches the lower uterine segment
	II	Reaches internal os of the cervix (marginal)
Major	III	Covers part of internal os (partial)
	IV	Completely covers the internal os (complete)

Women with pregnancies in which the placenta is low lying (less than 2 cm from the internal os) or praevia are recommended to give birth by caesarean section. Placental location is routinely determined at the time of the fetal anatomy scan at 18 to 22 weeks and may be found to be low lying or praevia at that stage ( Fig. 26.2 ). As the uterus grows from the lower segment upwards, the placenta appears to move upwards with advancing gestation, with resolution of low-lying placenta in 90% of cases before term. This is not a reflection of placental migration; rather, it is simply a feature of uterine growth. When a low-lying placenta is detected on ultrasound scanning early in pregnancy, it is necessary to repeat the scan early in the third trimester and then review the woman’s care if placenta praevia persists.

The risk of placenta praevia is of a sudden, unpredictable, major or massive haemorrhage. The woman’s care may be either as an inpatient or outpatient. Factors that will affect this decision include distance and transport availability to a hospital where facilities for resuscitation and birth are immediately available, number of episodes of bleeding and their severity, haematology results, and willingness to accept blood and/or blood products. Elective birth by caesarean section is usually planned for 36 to 37 weeks but will be considered earlier if there is a history of vaginal bleeding or other risk factors for pre-term birth.

Caesarean section in the presence of placenta praevia should be directly supervised by, or performed by, a senior obstetrician since a large blood loss is frequently encountered owing to the relatively poor capacity of the lower segment of the uterus to contract and, in many cases, the need to incise through the placenta to deliver the baby.

Placental Abruption

Placental abruption is defined as retroplacental haemorrhage (bleeding between the placenta and the uterus) as a result of some degree of placental separation prior to birth of the baby. The care of women with placental abruption depends on the amount of bleeding, presence or absence of maternal haemodynamic compromise, the maturity of the fetus and its condition. Separation of the placenta results in a reduced area for gas exchange between the fetal and maternal circulations, predisposing to fetal hypoxia and acidosis. It is crucial to remember that with placental abruption the amount of ‘revealed’ blood (bleeding from the vagina) may not reflect the total blood loss and that a woman may have considerable retroplacental bleeding without any external loss at all – a ‘concealed abruption’ ( Fig. 26.3 ).

Recognised risk factors for placental abruption include a history of a previous pregnancy affected by placental abruption and maternal cigarette smoking ( Table 26.2 ), 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. A brief episode of inpatient observation and often surveillance of subsequent fetal growth with ultrasound fetal biometry is appropriate. Repeated episodes of placental abruption may lead to a decision to deliver early.

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

If intrauterine fetal death is diagnosed, vaginal birth is to be preferred, if safe to do so, although the woman’s preferences should always be considered. However, in such a situation, it is likely that there will have been a major degree of blood loss. Hypovolaemic shock may develop and may progress to multisystem organ failure if not corrected. In addition, release of thromboplastins from the damaged placenta may lead to disseminated intravascular coagulation (DIC) with depletion of platelets, fibrinogen and other clotting factors. Therefore, waiting for the baby to be born vaginally carries risks, and caesarean birth may occasionally be indicated to minimise these systemic maternal risks. Deciding on the appropriate mode of birth is further complicated by the risks of carrying out an operation in the presence of DIC.

Less severe degrees of placental separation can still be associated with fetal compromise. The woman usually describes pain and frequent contractions, the contractions precipitated by irritation of the myometrium from the retroplacental clot. The fetal heart rate will often show a suspicious or pathological pattern, which may progress to a fetal bradycardia and fetal death unless birth of the baby is expedited. Placental abruption predisposes the mother to PPH.

Unexplained Antepartum Haemorrhage

In approximately half of cases, a specific cause for APH is not found. Bleeding with no explanation is the most common clinical scenario. In the absence of maternal or fetal compromise, it is managed expectantly. Unexplained APH, especially if more than one episode (recurrent unexplained APH), is a recognised risk factor for subsequent fetal growth restriction; additional ultrasound surveillance is recommended.