Antepartum haemorrhage

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Chapter 13 Antepartum haemorrhage

CHAPTER CONTENTS

Placenta praevia 113

Symptoms, signs and diagnosis 113
Management 113
Complications 115
Placenta accreta 115
Placental abruption 115

Aetiology and pathology of abruptio placentae 115
Signs, symptoms and treatment of antepartum haemorrhage 115
Management of abruptio placentae 116
Maternal and fetal loss 116

Antepartum haemorrhage is defined as significant bleeding from the birth canal occurring after the 20th week of pregnancy. The causes and proportions of cases of antepartum haemorrhage are shown in Table 13.1. In fewer than 0.05% of cases the bleeding is due to a cervical lesion, such as a cervical polyp, or rarely, a cervical carcinoma.

Table 13.1 The incidence of the causes of antepartum haemorrhage

  INCIDENCE (%)
Placenta praevia 0.5
Placental abruption
Mild or indeterminate 3.0
Moderate grade 0.8
Severe grade 0.2
Cervical bleeding 0.05

PLACENTA PRAEVIA

In this condition the placenta is implanted, either partially or wholly, in the lower uterine segment and lies below (praevia) the fetal presenting part. The extent of implantation may be minor, in which case vaginal birth is possible, or major, when it is not (Fig. 13.1).

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Fig. 13.1 Degrees of placenta praevia.

Placenta praevia occurs in 0.5–2.0 % of all pregnancies, and accounts for 20% of all cases of antepartum haemorrhage. The incidence has increased between two- and threefold over the past 20 years. It is three times as common in multiparous women as in primiparae. The incidence increases with each previous caesarean section. The incidence in women who have not had a previous caesarean is 0.3%, after one is 0.8%, after two is 2.0%, and after three or more is 4.2%. The risk is also increased when a submucous fibroid is present.

The bleeding occurs when the lower uterine segment is increasing in length, and shearing forces between the trophoblast and the maternal blood sinuses occur. The first episode of bleeding occurs after the 36th gestational week in 60% of cases, between the 32nd and 36th weeks in 30%, and before the 32nd week in 10%.

Symptoms, signs and diagnosis

The bleeding is painless, causeless and recurrent. The presenting part is usually high and often not central to the pelvic brim. The diagnosis is made should an ultrasound image show that the placenta is praevia (Figs 13.2, 13.3).

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Fig. 13.2 Grade 2 placenta praevia reaching 1.6 cm from internal os.

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Fig. 13.3 Vaginal scan showing grade 4 placenta praevia covering internal os.

If a routine ultrasound examination is made at 18 weeks the report may show that there is a low-lying placenta, but in over 85% the placenta will be normally situated by the time of delivery, as the lower uterine segment does not develop fully until late in the third trimester. A further ultrasound examination should be made at about the 34th week, or earlier if vaginal bleeding occurs.

Management

The first episode of significant bleeding usually occurs in the patient’s home and is usually not heavy. The patient should be admitted to hospital and no vaginal examination made, as this may start torrential bleeding. In hospital the patient’s vital signs are checked, the amount of blood loss assessed and blood cross-matched. Heavy blood loss may require transfusion. The abdomen is palpated gently to determine the gestational age of the fetus, and its presentation and position. An ultrasound examination is made soon after admission, to confirm the diagnosis. Further management depends on the severity of the bleeding and the gestational age of the fetus.

In cases of severe bleeding, urgent treatment to deliver the baby (and the placenta) is required, irrespective of the gestational age of the fetus. If the bleeding is less severe, expectant treatment is appropriate if the fetal gestational age is less than 36 weeks. As the bleeding tends to recur, serum should be held in the blood bank in case an urgent transfusion is required and the safest option for the woman is to remain in hospital. In selected cases where there is no further bleeding for 4–7 days and the woman can readily return to hospital if she has further bleeding then she may be allowed to rest at home. An episode of severe bleeding may lead to urgent delivery, but in most cases the pregnancy can continue until term (37 or more weeks). All but the most minor degrees of placenta praevia will require delivery by caesarean section. Blood should be cross-matched and readily available during delivery and the immediate puerperium.

Complications

Episodes of heavy bleeding may occur at any time, during which the fetus may die from hypoxia. Following the birth, postpartum haemorrhage may occur because the trophoblast has invaded the poorly supported veins of the lower uterine segment. In most cases the haemorrhage ceases after the administration of oxytocics, but occasionally the bleeding cannot be staunched. Compression of the placental bed by an intrauterine balloon catheter may control the bleeding, otherwise caesarean hysterectomy is required.

The perinatal mortality is less than 50 per 1000 and primarily due to prematurity. The maternal mortality is low, provided the case is managed by an experienced obstetrician and no vaginal examination is performed before admission to hospital.

PLACENTA ACCRETA

Morbid adherence of the placenta occurs in 1/1500 to 1/2500 pregnancies and the incidence is reported to be increasing. One likely reason is the rising caesarean section rate. If the placenta implants over a uterine scar from a previous caesarean section, the trophoblast can penetrate through the scarred decidua and myometrium, becoming morbidly adherent. Unless the area of adherence is small, conservative management is not usually possible and the woman will require immediate caesarean hysterectomy to preserve her life. The haemorrhage is frequently accompanied by disseminated intravascular coagulopathy, and this should be anticipated in any woman who has had a previous caesarean section and has an anterior low-lying placenta. The risk of placenta praevia or accreta rises from 4% if there has not been a previous caesarean section to 14% after one, 35% after two, and 50% after three.

PLACENTAL ABRUPTION (ACCIDENTAL HAEMORRHAGE)

The term ‘accidental haemorrhage’ derives from an observation made in 1775 that in placenta praevia haemorrhage is inevitable, whereas in the other group of antepartum haemorrhage it is due to some ‘accidental’ circumstance. About 4% of pregnant women have a placental abruption, which can be subdivided into three groups. In the first the bleeding is slight, and when the placenta is examined after the birth no retroplacental bleeding can be observed. This group is classified as antepartum haemorrhage of unknown aetiology. It accounts for 75% of cases of accidental haemorrhage.

In the second and third groups there is evidence of retroplacental bleeding. The amount of blood lost to the circulation may be moderate or severe. These two groups are classified as abruptio placentae. Abruptio placentae accounts for 25% of cases of accidental haemorrhage. In four-fifths of cases of abruptio placentae the amount of blood lost to the circulation is moderate (<1500 mL), and in one-fifth the blood loss is severe (>1500 mL).

Aetiology and pathology of abruptio placentae

The aetiology is obscure, the only relevant associations being multiparity, cigarette smoking, cocaine use, multiple pregnancy, and polyhydramnios. Hypertensive diseases in pregnancy are associated with abruptio placentae in about 15% of cases, but it is not clear whether the hypertension is an aetiological factor. Occasionally it can result from direct trauma to the maternal abdomen or by compression of the uterus onto the sacral promontory during deceleration in a motor vehicle accident.

The cause of the retroplacental bleeding is damage to the walls of the maternal venous sinuses supplying the placental bed. The bleeding spreads and causes detachment of the placenta to varying degrees. The blood then trickles down between the uterine decidua and the amniotic sac to appear in the vagina and vulva (revealed haemorrhage), or is retained behind the placenta (concealed haemorrhage). In a few cases of severe bleeding the blood is forced by intrauterine pressure between the myometrial fibres towards the serosal layer of the uterus. If the amount of blood is large, the uterus has the appearance of a bruised, oedematous organ, described as apoplexie utéroplacentaire, or couvelaire uterus. This is a rare occurrence in today’s obstetric practice.

In severe cases of abruptio placentae shock may result from the distraction and separation of the myometrial fibres. Another complication is the release into the circulation of thromboplastins from the damaged vessels, which cause widespread intravascular coagulation. The microthrombi are dissolved by fibrinogens, mainly plasmin, with the release of fibrin degradation products and the possible development of consumptive coagulopathy. In severe cases some microthrombi escape lysis and are deposited in the endothelium of the vessels supplying the glomeruli of the kidneys. This may lead to tubular necrosis and oliguria or anuria.

Signs, symptoms and treatment of antepartum haemorrhage

The symptomatology is related to the degree of bleeding and the extent of placental detachment (Table 13.2).

Table 13.2 Comparison of the clinical picture in the various grades of accidental haemorrhage

image

Slight haemorrhage

The amount of blood lost is less than 500 mL and there is no disturbance of the maternal or fetal condition. An ultrasound examination shows that the placenta is not lying in the lower uterine segment and no retroplacental clots can be seen. If the patient has been admitted to hospital she may go home once the bleeding ceases or, if the pregnancy has advanced to 37 weeks, she may choose to have labour induced by amniotomy, provided that the condition of the cervix warrants this.

Abruptio placentae: moderate placental detachment and haemorrhage

Usually at least one-quarter of the placenta has become detached and more than 1000 mL of blood have been lost to the circulation. The woman complains of abdominal pain and the uterus is tender because blood has infiltrated between its muscle fibres. The patient may be shocked, with a high pulse rate, but paradoxically in 5% of cases the pulse rate is within the normal range until delivery, at which time it rises precipitously. The fetus is hypoxic and may show abnormal heart rate patterns on a cardiotocogram.

Abruptio placentae: severe placental detachment and haemorrhage

In cases of severe placental detachment at least 1500 mL of blood have been lost to the circulation. The woman is usually in shock; her uterus is firm to hard and very tender. The fetus is almost always dead. As pre-eclampsia is associated with only about one-third of cases, the blood pressure may be in the normal range in spite of the shock. Most coagulopathies occur in this group.

Management of abruptio placentae

Management consists of restoring the blood lost, prevention of coagulopathy and monitoring urinary output:

• At least 1500 mL of blood should be transfused in cases of moderate detachment, and 2500 mL in cases classified as severe detachment. The first 500 mL are transfused rapidly. Rapid blood transfusion prevents renal ‘shutdown’ and anuria. The central venous pressure is monitored and the remainder of the transfusion adjusted accordingly. The blood loss and the height of the fundus are monitored.
• Venous blood is examined 2-hourly for evidence of coagulopathy and, if present, this is treated. Adequate rapid transfusion and amniotomy or caesarean section usually prevent it from occurring.
• Urine output is measured 2-hourly. Oliguria may occur, but diuresis follows the birth provided that sufficient blood has been transfused.
• If the fetus is alive the decision has to be made whether to perform a caesarean section or the artificial rupture of the amniotic membranes (ARM). If the latter is chosen the circulating blood volume must first be restored. The fetal heart is monitored, and if the fetal CTG shows non-reassuring patterns a caesarean section is performed; however, it is imperative that first the mother is adequately resuscitated. If there are ominous CTG abnormalities the long-term prognosis for the baby is poor.

Maternal and fetal loss

Maternal mortality depends on the speed and adequacy of treatment. Today, few women should die from abruptio placentae. Fetal mortality depends on the degree of placental separation.

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