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Pre-eclampsia

Extracted from Survival Guide to Midwifery, 2nd Edition (2012) Diane M. Fraser and Margaret A. Cooper, Oxford; Churchill Livingstone: 2012. Courtesy Elsevier

Pre-eclampsia is a condition peculiar to pregnancy, which is characterised by hypertension, proteinuria and systemic dysfunction.

Pre-eclampsia is diagnosed on the basis of hypertension with proteinuria, when proteinuria is measured as > 1 + on dipstick or > 0.3 g/L of protein in a random clean catch specimen or an excretion of 0.3 g protein/24 hours

In the absence of proteinuria, pre-eclampsia is suspected when hypertension is accompanied by symptoms including:

  • Headache
  • Blurred vision
  • Abdominal/epigastric pain, or
  • Altered biochemistry: specifically, low platelet counts, abnormal liver enzyme levels

     

These signs and symptoms, together with blood pressure above 160 mmHg systolic or above 110 mmHg diastolic and proteinuria of 2 + or 3 + on a dipstick, demonstrate the more severe form of the disease Early detection and appropriate management can minimise the severity of the condition. A comprehensive history will identify:

  • Adverse social circumstances or poverty, which could prevent the woman from attending for regular antenatal care
  • The mother's age and parity
  • Primipaternity and partner-related factors
  • A family history of hypertensive disorders
  • A past history of pre-eclampsia
  • The presence of underlying medical disorders: for example, renal disease, diabetes, systemic lupus erythematosus (SLE) and thromboembolic disorders.

     

The two essential features of pre-eclampsia, hypertension and proteinuria, are assessed for at regular intervals throughout pregnancy. Diagnosis is usually based on the rise in blood pressure and the presence of proteinuria after 20 weeks' gestation.

Blood pressure measurement

The mother's blood pressure is taken early in pregnancy to compare with all subsequent recordings, taking into account the normal pattern in pregnancy. It is important to consider several factors in assessing blood pressure. Blood pressure machines should be calibrated for use in pregnancy and regularly maintained. Blood pressure can be overestimated as a result of using a sphygmomanometer cuff of inadequate size relative to the arm circumference. The length of the bladder should be at least 80% of the arm circumference. Two cuffs should be available with inflation bladders of 35 cm for normal use and 42 cm for large arms. Rounding off of blood pressure measurements should be avoided and an attempt should be made to record the blood pressure as accurately as possible to the nearest 2 mmHg. The use of Korotkoff V (disappearance of sound) as a measure of the diastolic blood pressure has been found to be easier to obtain, more reproducible and closer to the intra-arterial pressure; therefore this reading should be used unless the sound is near zero, in which case Korotkoff IV (muffling sound) should be used instead.

Urinalysis

Proteinuria in the absence of urinary tract infection is indicative of glomerular endotheliosis. The amount of protein in the urine is frequently taken as an index of the severity of pre-eclampsia. A significant increase in proteinuria, coupled with diminished urinary output, indicates renal impairment. A 24-hour urine collection for total protein measurement will be required to be certain about the presence or absence of proteinuria and to provide an accurate quantitative assessment of protein loss. A finding of >300 mg/24 hours is considered to be indicative of mild to moderate pre-eclampsia; >3 g/24 hours is considered to be severe.

Oedema

The sudden severe widespread appearance of oedema is suggestive of pre-eclampsia or some underlying pathology and further investigations are necessary. This oedema pits on pressure and may be found in non-dependent anatomical areas such as the face, hands, lower abdomen, and vulval and sacral areas.

Laboratory tests

Alterations in the following haematological and biochemical parameters are suggestive of pre-eclampsia:

  • Increased haemoglobin (Hb) and haematocrit levels
  • Thrombocytopenia
  • Prolonged clotting times
  • Raised serum creatinine and urea levels
  • Raised serum uric acid level
  • Abnormal liver function tests, particularly raised transaminases

     

Care and management

The aim of care is to monitor the condition of the woman and her fetus and, if possible, to prevent the hypertensive disorder worsening by using appropriate interventions and treatment. The objective is to prolong the pregnancy until the fetus is sufficiently mature to survive, while safeguarding the mother's life.

Antenatal care

Rest It is preferable for the woman to rest at home and to be visited regularly by the midwife or GP. When proteinuria develops in addition to hypertension, the risks to the mother and fetus are considerably increased. Admission to hospital is required to monitor and evaluate the maternal and fetal condition.

Diet There is little evidence to support dietary intervention for preventing or restricting the advance of pre-eclampsia.

Weight gain Weight gain may be useful for monitoring the progression of pre-eclampsia in conjunction with other parameters.

Blood pressure and urinalysis The blood pressure is monitored daily at home or every 4 hours when in hospital. Urine should be tested for protein daily. If protein is found in a midstream specimen of urine, a 24-hour urine collection is instigated in order to determine the amount of protein. The level of protein indicates the degree of vascular damage. Reduced kidney perfusion is indicated by:

  • Proteinuria
  • Reduced creatinine clearance
  • Increased serum creatinine and uric acid.

     

Abdominal examination

This is carried out daily. Any discomfort or tenderness may be a sign of placental abruption. Upper abdominal pain is highly significant and indicative of HELLP syndrome (see HELLP syndrome) associated with fulminating (rapid-onset) pre-eclampsia. [italics]Fetal assessmentIt is advisable to undertake a biophysical profile in order to determine fetal health and wellbeing. This is done by the use of:

  • Kick charts
  • Cardiotocography (CTG) monitoring
  • Serial ultrasound scans to check for fetal growth
  • Assessment of liquor volume and fetal breathing movements or Doppler flow studies, or both, to determine placental blood flow.

     

Laboratory studies

These include:

  • Full blood count, platelet count and clotting profile
  • Urea and electrolytes
  • Creatinine and liver function tests, including albumin levels.

In severe pre-eclampsia blood samples should be taken every 12-24 hours.

Antihypertensive therapy The use of antihypertensive therapy as prophylaxis is controversial, as this shows no benefit in significantly prolonging pregnancy or improving maternal or fetal outcome. Its use is, however, advocated as short-term therapy in order to prevent an increase in blood pressure and the development of severe hypertension, thereby reducing the risk to the mother of cerebral haemorrhage. Methyldopa is the most widely used drug in women with mild to moderate gestational hypertension and appears to be safe and effective for both mother and fetus. Alpha and beta blockers such as labetalol are considered safe in pregnancy. Atenolol used over the long term is not recommended as it may cause significant fetal growth restriction.

 

Antithrombotic agents

Early activation of the clotting system may contribute to the later pathology of pre-eclampsia; as a result the use of anticoagulants or antiplatelet agents has been considered for the prevention of pre-eclampsia and fetal growth restriction. Aspirin is thought to inhibit the production of the platelet-aggregating agent, thromboxane A2; it is recommended for women at risk from 12 weeks.

Intrapartum care

It is essential to monitor the maternal and fetal condition carefully.

Vital signs Blood pressure is measured half-hourly, or every 15-20 minutes in severe pre-eclampsia. Because of the potentially rapid haemodynamic changes in pre-eclampsia, a number of authors recommend the measurement of the mean arterial pressure (MAP). MAP reflects the systemic perfusion pressure, and therefore the degree of hypovolaemia, whereas manual measurement of diastolic pressure alone is a better indicator of the degree of hypertension. Observation of the respiratory rate (> 14/min) will be complemented with pulse oximetry in severe pre-eclampsia; this gives an indication of the degree of maternal hypoxia. Temperature should be recorded as necessary. In severe pre-eclampsia, examination of the optic fundi can give an indication of optic vasospasm. Cerebral irritability can be assessed by the degree of hyper-reflexia or the presence of clonus (significant if more than 3 beats).

Fluid balance The reduced intravascular compartment in pre-eclampsia, together with poorly controlled fluid balance, can result in circulatory overload, pulmonary oedema, acute respiratory distress syndrome and ultimately death. In severe pre-eclampsia a central venous pressure (CVP) line may be considered; measurements are taken hourly. If the value is >10 mmHg, then 20 mg furosemide should be considered. Intravenous fluids are administered using infusion pumps; the total recommended fluid intake in severe pre-eclampsia is 85 ml/h. Oxytocin should be administered with caution, as it has an antidiuretic effect. Urinary output should be monitored and urinalysis undertaken every 4 hours to detect the presence of protein, ketones and glucose. In severe pre-eclampsia a urinary catheter should be in situ and urine output is measured hourly; a level > 30 ml/h reflects adequate renal function.

Plasma volume expansion Although women with pre-eclampsia have oedema, they are hypovolaemic. The blood volume of women with pre-eclampsia is reduced, as shown by a high haemoglobin (Hb) concentration and a high haematocrit level. This results in movement of fluid into the extravascular compartment, causing oedema. The oedema initially occurs in dependent tissues, but as the disease progresses oedema occurs in the liver and brain.

Pain relief Epidural analgesia may procure the best pain relief, reduce the blood pressure and facilitate rapid Caesarean section, should the need arise. It is important to ensure a normal clotting screen and a platelet count >100 × 109/l prior to insertion of the epidural.

Fetal condition The fetal heart rate should be monitored closely. Deviations from the normal must be reported and acted upon.

Birth plan When the second stage commences, the obstetrician and paediatrician should be notified. A short second stage may be prescribed, depending on the maternal and fetal conditions. If the maternal or fetal condition shows significant deterioration during the first stage of labour, a Caesarean section will be undertaken. Oxytocin is the preferred agent for the management of the third stage of labour. Ergometrine and syntometrine will cause peripheral vasoconstriction and increase hypertension; they should therefore not normally be used in the presence of any degree of pre-eclampsia, unless there is severe haemorrhage.

Postpartum care

The maternal condition should continue to be monitored at least every 4 hours for the next 24 hours or more following childbirth, as there is still a potential danger of the mother developing eclampsia.

Signs of impending eclampsia

  • A sharp rise in blood pressure
  • Diminished urinary output
  • Increase in proteinuria
  • Headache, which is usually severe, persistent and frontal in location
  • Drowsiness or confusion
  • Visual disturbances, such as blurring of vision or flashing lights
  • Epigastric pain
  • Nausea and vomiting

     

The aim of care at this time is to prevent death of the mother and fetus by controlling hypertension, inhibiting convulsions and preventing coma.

The Practising Midwife featured article

Midwifery Basics: Blood tests for investigating maternal wellbeing: Blood tests for investigating pre-eclampsia 2011; 14(3): 40 -46. Author: Joyce Cowan

Further reading/resources

Payne J. (2016) Pre-eclampsia and eclampsia. (Professional reference). http://patient.info/doctor/pre-eclampsia-and-eclampsia

NICE (2010). Hypertension in pregnancy: diagnosis and management. Clinical guideline 107. https://www.nice.org.uk/guidance/cg107

Action on pre-eclampsia (APEC) (2004) PRECOG: The Pre-eclampsia Community Guideline http://action-on-pre-eclampsia.org.uk/wp-content/uploads/2012/07/PRECOG-Community-Guideline.pdf

Action on pre-eclampsia (ACOG) (2014)* e-learning package for midwives. http://action-on-pre-eclampsia.org.uk/E-learning/Elearning_Oct2014.pdf *This e-learning resource is currently being updated and a new version is expected shortly

 

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