Pre-eclampsia

From Ganfyd

Pre-eclampsia is the maternal gestational onset of hypertension and proteinuria.

Clinical definition

A working definition is after 20 weeks of gestation:

• Hypertension -systolic blood pressure ≥ 140 mmHg and/or diastolic blood pressure ≥ 90 mmHg, or both (in women known to be previously normotensive)
• Proteinuria > 300 mg/24 hours

Severe Pre-eclampsia: EITHER

• Proteinuria > 5g/24 hours (or 3+ on dipstick)
• Hypertension - systolic > 160mmHg or diastolic > 110mmHg on 2 occasions

OR

• Protenuria > 5g/24 hours
• Hypertension - diastolic > 100mmHg
• 2 Further clinical symptoms or HELLP syndrome

Incidence

• 2-8% of first time pregnant mothers^[1]
• Marked variation in different populations
• Higher in nulliparous than multiparous women
• Risk factors:
  • Chronic hypertension
  • Maternal age at first pregnancy (over 35 years)
  • Nephropathy
  • Thrombophilia
  • Multiple gestation
  • Previous preeclampsia in pregnancy
• Risk reduced by a third in smokers but with increased risk to fetus !

Aetiology

The cause is not fully understood but can be described as abnormal placentation with placental mediators targeting the maternal endothelium. There is defective invasion of trophoblast cells and remodelling of the uterine vasculature with reduced utero-placental perfusion and consequential placental ischaemia. There is activation of maternal vasoconstriction and damage of endothelial cells by several mechanisms including reactive oxygen species and defective synthesis of nitric oxide.

Associations

• Increased perinatal mortality
• Placental abruption
• HELLP syndrome (haemolysis, elevated liver enzymes, low platelets)
• Eclampsia
• Increased risk eclampsia
• Raised asymmetric dimethyl arginine, a competitive inhibitor of nitric oxide synthase
• Raised soluble fms-like tyrosine kinase 1 (soluble VEGFR-1 , vascular endothelial growth factor receptor-1)
• Raised soluble endoglin, which impairs activation of nitric oxide synthase mediated by transforming growth factor β

Clinical Features

Symptoms

Pre-eclampsia is often asymptomatic, and symptoms are often vague and non-specific. This rare condition is one reason why abdominal pain must be taken seriously in any pregnant woman. By definition, if pre-eclampsia progresses to convulsions, it is termed "eclampsia".

• Stridor (from laryngeal oedema)
• Dyspnoea (from pulmonary oedema)
• Headache
• Epigastric pain
• Right Upper Quadrant pain
• Peripheral Oedema

Signs

Cardiac

• Hypertension
• Increased sensitivity to catecholamines and vasopressors
• Increased Systemic Vascular Resistance
• Dissociation between Central Venous Pressure and *Pulmonary capillary Wedge Pressure

Respiratory

• Tachypnoea
• Desaturation

Renal

• Proteinuria > 300mg/24hrs
• Oliguria < 400ml/day
• High creatinine
• Plasma uric acid > 0.35

CNS

• Hyperreflexia
• Clonus
• May progress to eclampsia

Fetus

• Intrauterine growth retardation
• Oligohydramnios

Particular features of severe pre-eclampsia

• BP 160/110
• proteinuria 5g/24hrs
• oliguria < 400ml/24hrs
• pulmonary oedema
• cerebrovascular haemorrhage, or cerebral oedema
• epigastric/RUQ pain
• hepatic rupture
• platelets < 100 x10^9/litre

Prevention

• Low dose aspirin
  • Decreases the risk of recurrence of preeclampsia by 10%, of prematurity by 8% and of perinatal mortality by 14%.
• Calcium supplements in third word population
• Possibly L-arginine with vitamins^[2]
• Antioxidant vitamins do not work^[3][4]

Treatment

• Hypotensive agents
• Magnesium sulfate in severe pre-eclampsia prevents eclampsia^[5] and has good long term safety data^[6]

Also see Eclampsia

References