What are the key diagnostic criteria for pre-eclampsia in a pregnant patient presenting with hypertension?

Key diagnostic criteria for pre-eclampsia in a pregnant patient presenting with hypertension are:

• New onset of hypertension after 20 weeks of pregnancy, defined as systolic blood pressure over 140 mmHg or diastolic blood pressure over 90 mmHg.
• Coexistence of one or more of the following new-onset conditions:
• Proteinuria, defined as a urine protein:creatinine ratio of 30 mg/mmol or more, or albumin:creatinine ratio of 8 mg/mmol or more, or at least 1 g/litre (2+) on dipstick testing.
• Other maternal organ dysfunction, including:
• Renal insufficiency (serum creatinine 90 micromol/litre or more).
• Liver involvement (elevated transaminases over 40 IU/litre with or without right upper quadrant or epigastric pain).
• Neurological complications such as eclampsia, altered mental status, blindness, stroke, clonus, severe headaches, or persistent visual scotomata.
• Haematological complications such as thrombocytopenia (platelet count below 150,000/microlitre), disseminated intravascular coagulation, or haemolysis.
• Uteroplacental dysfunction such as fetal growth restriction, abnormal umbilical artery Doppler waveform analysis, or stillbirth.

These criteria are based on NICE guidelines for hypertension in pregnancy and are used to distinguish pre-eclampsia from gestational hypertension and other hypertensive disorders in pregnancy.