How do health care providers diagnose preeclampsia, eclampsia, and HELLP syndrome?

A health care provider will check a pregnant woman's blood pressure and urine during each prenatal visit. If the blood pressure reading is considered high (140/90 or higher), especially after the 20th week of pregnancy, the health care provider will likely perform blood tests and more extensive lab tests to look for extra protein in the urine (called proteinuria) as well as other symptoms.

The American College of Obstetricians and Gynecologists provides the following criteria for a diagnosis of gestational hypertension, preeclampsia, eclampsia, and HELLP syndrome.

Gestational hypertension is diagnosed if a pregnant woman has high blood pressure but no protein in the urine. Gestational hypertension occurs when women whose blood pressure levels were normal before pregnancy develop high blood pressure after 20 weeks of pregnancy. Gestational hypertension can progress into preeclampsia.¹

Mild preeclampsia is diagnosed when a pregnant woman has:^2,3

• Systolic blood pressure (top number) of 140 mmHg or higher or diastolic blood pressure (bottom number) of 90 mmHg or higher and either
  • Urine with 0.3 or more grams of protein in a 24-hour specimen (a collection of every drop of urine within 24 hours) or a protein-to-creatinine ratio greater than 0.3 
    or
  • Blood tests that show kidney or liver dysfunction
  • Fluid in the lungs and difficulty breathing
  • Visual impairments

Severe preeclampsia occurs when a pregnant woman has any of the following:

• Systolic blood pressure of 160 mmHg or higher or diastolic blood pressure of 110 mmHg or higher on two occasions at least 4 hours apart while the patient is on bed rest
• Urine with 5 or more grams of protein in a 24-hour specimen or 3 or more grams of protein on 2 random urine samples collected at least 4 hours apart
• Test results suggesting kidney or liver damage—for example, blood tests that reveal low numbers of platelets or high liver enzymes
• Severe, unexplained stomach pain that does not respond to medication
• Symptoms that include visual disturbances, difficulty breathing, or fluid buildup⁴

Eclampsia occurs when women with preeclampsia develop seizures. The seizures can happen before or during labor or after the baby is delivered. 

HELLP syndrome is diagnosed when laboratory tests show hemolysis (burst red blood cells release hemoglobin into the blood plasma), elevated liver enzymes, and low platelets. There also may or may not be extra protein in the urine.⁵

Some women may also be diagnosed with superimposed preeclampsia—a situation in which the woman develops preeclampsia on top of high blood pressure that was present before she got pregnant. Health care providers look for an increase in blood pressure and either protein in the urine, fluid buildup, or both for a diagnosis of superimposed preeclampsia.

In addition to tests that might diagnose preeclampsia or similar problems, health care providers may do other tests to assess the health of the mother and fetus, including:

• Blood tests to see how well the mother's liver and kidneys are working
• Blood tests to check blood platelet levels to see how well the mother's blood is clotting
• Blood tests to count the total number of red blood cells in the mother's blood
• A maternal weight check
• An ultrasound to assess the fetus's size
• A check of the fetus's heart rate
• A physical exam to look for swelling in the mother's face, hands, or legs as well as abdominal tenderness or an enlarged liver