What the diagnosis means in guideline terms

NICE guideline NG133 defines pre-eclampsia as "new onset of hypertension (over 140 mmHg systolic or over 90 mmHg diastolic) after 20 weeks of pregnancy and the coexistence of 1 or more of the following new-onset conditions": proteinuria, or maternal organ dysfunction, or uteroplacental dysfunction.

Two things follow from that definition. First, protein in the urine is not required. NICE lists renal insufficiency, liver involvement, neurological complications, haematological complications and uteroplacental dysfunction - including fetal growth restriction and abnormal umbilical artery Doppler - as alternatives. Second, the diagnosis is a combination, which is why one high reading at one appointment is not usually the end of the story.

The numbers NICE attaches to those categories are worth having in front of you when results are read out: proteinuria means a urine protein:creatinine ratio of 30 mg/mmol or more, or an albumin:creatinine ratio of 8 mg/mmol or more, or at least 1 g/litre (2+) on dipstick; renal insufficiency means creatinine 90 micromol/litre or more; liver involvement means transaminases over 40 IU/litre; thrombocytopenia means a platelet count below 150,000 per microlitre.

Mild, severe, and why the words matter

NICE defines hypertension as 140/90 mmHg or higher and severe hypertension as "over 160 mmHg systolic or over 110 mmHg diastolic". Severe pre-eclampsia is severe hypertension that does not respond to treatment, or is accompanied by recurring severe headaches, visual scotomata, nausea or vomiting, epigastric pain, oliguria, or deteriorating blood tests.

For scale, the RCOG says pre-eclampsia "is a condition that affects between 1-5 in 100 pregnant women", that it affects "up to 5 in 100 women during their first pregnancy and less than 2 in 100 in their second", and that "around one in 200 women develop severe pre-eclampsia, which can be life-threatening for both you and your baby". Eclampsia - a seizure - is rarer still, "affecting only one in 3000 pregnancies in the UK".

The monitoring schedule

NG133 sets this out in a table rather than leaving it to local habit. For pre-eclampsia without severe hypertension:

Blood pressure: at least every 48 hours, more often if you are admitted.
Blood tests: full blood count, liver function and renal function twice a week.
Dipstick proteinuria: only repeated if clinically indicated. Once pre-eclampsia is diagnosed, repeat protein measurements do not add much.
Ultrasound: at diagnosis, then repeated every 2 weeks if normal. A cardiotocograph at diagnosis, then only if clinically indicated.

If you have severe hypertension you are admitted, blood pressure is taken every 15 to 30 minutes until it is below 160/110 mmHg and then at least four times daily, and the blood tests move to three times a week.

What triggers admission

Recommendation 1.5.2 lists the concerns that should prompt admission, and they are concrete: sustained systolic blood pressure of 160 mmHg or higher; a new and persistent rise in creatinine to 90 micromol/litre or more; a rise in alanine transaminase over 70 IU/litre or twice the upper limit of normal; a fall in platelet count under 150,000 per microlitre; signs of impending eclampsia or pulmonary oedema; suspected fetal compromise.

NICE also suggests clinicians "consider using either the fullPIERS or PREP-S validated risk prediction models" to guide where you are cared for. PREP-S is only for use up to 34 weeks, and neither model predicts outcomes for the baby.

What the treatment does, and what it does not

Labetalol is offered first, with nifedipine if labetalol is unsuitable and methyldopa if neither is. The target once you are on treatment is "a BP of 135/85 mmHg or less", and pharmacological treatment is offered if blood pressure remains above 140/90 mmHg.

Be clear about what this achieves. Lowering blood pressure reduces the risk of stroke and other consequences of the pressure itself. It does not treat the placental problem underneath. As the RCOG puts it, "the only way to cure pre-eclampsia is for your baby to be born". Magnesium sulfate is used to reduce the chance of an eclamptic fit, and to treat one, not to lower blood pressure.

Placental growth factor (PlGF)-based testing is offered on one occasion between 20 weeks and 36 weeks plus 6 days where pre-eclampsia is suspected. It is a rule-out test: a normal result makes pre-eclampsia unlikely in the short term.

Timing of birth

NG133 table 3 divides this by gestation. Before 34 weeks: continue surveillance unless there are indications for planned early birth, and offer intravenous magnesium sulfate and a course of antenatal corticosteroids. From 34 weeks to 36 weeks plus 6 days: continue surveillance unless indicated, weighing your condition, the baby's condition and neonatal unit availability. From 37 weeks: "Initiate birth within 24 to 48 hours."

The thresholds for planning birth before 37 weeks are listed in recommendation 1.5.7 and include blood pressure that cannot be controlled with three or more classes of antihypertensive, maternal oxygen saturation below 90%, progressive deterioration in liver or renal function or platelets, ongoing neurological features, placental abruption, and reversed end-diastolic flow on umbilical artery Doppler.

After birth, and afterwards

Pre-eclampsia can begin or worsen after delivery. If you did not need blood pressure medication, NICE asks for blood pressure at least four times a day as an inpatient, at least once between day 3 and day 5, and on alternate days until normal if days 3 to 5 were abnormal. Treatment is started if blood pressure reaches 150/100 mmHg or higher. If you were on treatment, it is reduced if blood pressure falls below 130/80 mmHg.

You should be asked about severe headache and epigastric pain every time your blood pressure is taken. Everyone who has had pre-eclampsia is offered a medical review 6 to 8 weeks after the birth. The RCOG is direct about the long game: "If you have pre-eclampsia you are at more risk of developing high blood pressure, stroke and heart disease in later life." That review is where that conversation starts.

Pre-eclampsia