Pre-eclampsia

Learning objectives

• Definition and signs and symptoms of pre-eclampsia
• Management of pre-eclampsia

Definition and mechanisms

• Pre-eclampsia is defined as new onset hypertension (systolic blood pressure ≥ 140 mmHg, diastolic blood pressure ≥ 90 mmHg, or both) accompanied by one or more of the following features at or after 20 weeks of gestation:
  • Proteinuria:
    • Spot urinary protein creatinine ratio > 30 mg/mmol 
    • Or a 24-hour urine collection with > 300 mg of protein
  • Other material organ dysfunction, including:
    • Acute kidney injury
    • Liver involvement
    • Neurological complications: seizures, severe headaches, persistent visual scotomata, clonus, blindness, altered mental status, or stroke
  • Hematological complications: 
    • Thrombocytopenia
    • Disseminated intravascular coagulation (DIC)
    • Hemolysis
• Pre-eclampsia can be superimposed on women who have hypertension or proteinuria before 20 weeks of gestation and diagnosis can be more problematic in these patients
• Pre-eclampsia represents a potentially progressive clinical condition and the sub-categories ‘mild’ and ‘severe’ are no longer used
• HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome is potentially life-threatening to both mother and the baby and represents a severe form of pre-eclampsia
• Women may be critically unwell at presentation with placental abruption or DIC
• Left untreated, preeclampsia can lead to serious — even fatal — complications for both the mother and baby
  • Early delivery of the baby is often recommended 
• Pre-eclampsia affects 2–8% of pregnancies worldwide

Signs and symptoms

• Proteinuria or other signs of kidney problems
• Thrombocytopenia
• Increased liver enzymes 
• Severe headaches
• Changes in vision, including temporary loss of vision, blurred vision, or light sensitivity
• Shortness of breath
• Abdominal pain
• Nausea or vomiting

Severe pre-eclampsia

• Severe features associated with pre-eclampsia that warrant consideration of planned early birth before 37 weeks of gestation:
  • Inability to control maternal blood pressure despite using 3 or more classes of antihypertensives in appropriate doses
  • Progressive deterioration in liver function, renal function, hemolysis, or platelet count
  • Maternal pulse oximetry less than 90% on air
  • Ongoing neurological features, such as severe intractable headache, repeated visual scotomata, or eclampsia
  • Placental abruption
  • Reversed end-diastolic flow in the umbilical artery Doppler velocimetry, a non-reassuring cardiotocograph or stillbirth

Causes

• Abnormal placentation
• Immunological factors
• Prior or existing maternal pathology (see risk factors)
• Dietary actors such as low dietary calcium intake
• Environmental factors such as air pollution

Risk factors

Prevention

• Daily intake of 75-150 mg aspirin from 12 weeks until 36-37 weeks of gestation for any woman with one high, or two or more moderate risk factors
• Calcium supplementation (> 1 g/day) in case of low calcium dietary intake

Diagnosis

• Blood pressure ≥ 140 mmHg systolic or ≥ 90 mmHg diastolic on two separate readings taken at least four to six hours apart after 20 weeks of gestation in an individual with previously normal blood pressure
• An increase in systolic blood pressure of ≥ 30 mmHg or an increase in diastolic blood pressure of ≥ 15 mmHg in a woman with essential hypertension beginning before 20 weeks of gestational age
• Proteinuria ≥ 0.3 grams (300 mg) or more of protein in a 24-hour urine sample or a SPOT urinary protein to creatinine ratio ≥ 0.3
• Blood and urine analysis
• Fetal ultrasound

Management

Suggested reading

• Goddard, J., Wee, M.Y.K., Vinayakarao, L., 2020. Update on hypertensive disorders in pregnancy. BJA Education 20, 411–416.
• Leslie, D., Collis, R., 2016. Hypertension in pregnancy. BJA Education 16, 33–37.

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