Preeclampsia Diagnostic Criteria in Plain Numbers

A stem gives you a patient at 34 weeks with a blood pressure of 146 over 92 mmHg. That is not a diagnosis yet. The published criteria ask for four separate things to be true at once, and the item is usually testing whether you caught the one that is missing.

The numbers ACOG publishes

ACOG Practice Bulletin No. 222, printed in Obstetrics and Gynecology in June 2020, sets the threshold at a systolic pressure of at least 140 mmHg or a diastolic pressure of at least 90 mmHg. Either value crossing the line is enough on its own.

That little word does a lot of work. A patient at 138 over 94 mmHg has met the criterion on the diastolic side, and a patient at 152 over 84 mmHg has met it on the systolic side. Grade the two numbers separately.

Students lose points by treating the pair as a unit and waiting for both halves to rise. Nothing in the bulletin asks for that.

Two occasions, at least four hours apart

The same document requires those readings on two occasions at least 4 hours apart. One cuff reading in triage does not meet the definition, however alarming it looks on the monitor.

The interval exists because blood pressure is noisy. Pain, anxiety, a full bladder, a cuff that is too small, a patient who walked up two flights to the clinic. Any of those lifts a single reading, and the four hour gap is the published way of asking whether the elevation is real.

This is where a stem often hides its answer. If two readings sit ninety minutes apart, the criterion has not been met, and rechecking is the reasonable next move rather than escalating.

There is a documented exception at severe range pressures, where a four hour wait would delay treatment that should not wait. That exception has its own thresholds and its own logic, worked through in severe features and the shortcut for 160 over 110.

The twenty week boundary

Preeclampsia is defined after 20 weeks of gestation. Before that line, new hypertension in pregnancy points somewhere else, most often at chronic hypertension that was never measured before this pregnancy.

So gestational age is not background detail in these stems. It is a criterion. Find it in the first sentence of the case and write it down before you look at a single vital sign.

Nothing about the underlying pathology switches on at exactly 20 weeks. The boundary is a diagnostic convention that separates two different clinical stories, and the exam uses it as one.

Previously normotensive is doing real work

The fourth element is the phrase most people skim. The criteria describe new hypertension in a patient who was previously normotensive.

Someone with known chronic hypertension who arrives at 30 weeks with a pressure of 150 over 96 mmHg is not automatically meeting this definition. Her baseline was already high. The question for her is whether something new has been layered on top of that baseline, which is a different diagnostic conversation with different criteria.

So look for the prenatal record inside the stem. First trimester pressures, a documented history, an antihypertensive sitting on the medication list. Any of those changes what today's reading means.

Where proteinuria sits now

Proteinuria used to be the other half of the classic pair, and plenty of study material still teaches it that way. The current criteria do not require it. New hypertension plus any one of several other findings satisfies the definition without a single protein value in the chart.

That shift is large enough to deserve its own explanation, and the alternative findings are listed out in preeclampsia without proteinuria is still preeclampsia.

What the definition does not ask for

It is worth naming the absences. The four elements are a pressure threshold, a second reading at an interval, a gestational age, and a previously normotensive baseline. Symptoms are not among them.

Swelling is not in the criteria either, which surprises people who learned an older version of this. Ankle edema is ordinary in late pregnancy and it diagnoses nothing on its own.

Headache, visual change and epigastric pain matter enormously. They matter as severe features rather than as entry criteria, and that is a real distinction. They change how sick a diagnosed patient is, not whether the diagnosis has been reached.

Two different lists are running at once in this content area. Mixing them is one of the commonest ways a careful student loses an item.

Measurement technique sits underneath all of it

A criterion is only as good as the reading feeding it. A cuff that is too small reads high. A patient who has just hurried in from the car reads high. An arm dangling below heart level reads high.

None of that is trivia. If a stem tells you the pressure was taken the moment the patient arrived, or mentions a cuff that did not fit well, it has told you something about how much that number is worth.

Repeat the measurement properly before building anything on it. That is also, conveniently, exactly what the two occasion rule is asking you to do.

A worked reading

Take a patient at 26 weeks with no history of hypertension. Her pressure in the morning is 144 over 88 mmHg. Five hours later it is 148 over 92 mmHg.

Work the four elements in order. Gestational age is past 20 weeks. She was previously normotensive. Both readings cross 140 mmHg on the systolic side, and the two readings sit far enough apart to clear the four hour requirement.

All four elements are met. Now change one detail. Move the second reading to an hour after the first and the interval requirement fails, which makes a recheck the defensible answer rather than a diagnosis.

Change a different detail instead. Give her a documented history of chronic hypertension and the baseline element fails, which moves the question toward whether something has been superimposed on that history. Same two readings, same interval, different answer.

What to carry into the exam

Obstetric blood pressure items reward a checklist habit more than they reward recall. You are not being asked what preeclampsia is. You are being asked whether this patient, on this day, meets a published definition.

Four things. A number, a second number at an interval, a gestational age, and a baseline. Drop any one of them and the answer to the question in front of you changes.

The wider shape of obstetric items, and which numbers in this area are worth memorising at all, is mapped in maternity and newborn questions and what is really being tested.