Tests and diagnosis

By Mayo Clinic Staff

To diagnose preeclampsia, you have to have high blood pressure and one or more of the following complications after the 20th week of pregnancy:

  • Protein in your urine (proteinuria)
  • A low platelet count
  • Impaired liver function
  • Signs of kidney trouble other than protein in the urine
  • Fluid in the lungs (pulmonary edema)
  • New-onset headaches
  • Visual disturbances

Previously, preeclampsia was only diagnosed if a pregnant woman had high blood pressure and protein in her urine. However, experts now know that it's possible to have preeclampsia, yet never have protein in the urine.

A blood pressure reading in excess of 140/90 mm Hg is abnormal in pregnancy. However, a single high blood pressure reading doesn't mean you have preeclampsia. If you have one reading in the abnormal range — or a reading that's substantially higher than your usual blood pressure — your doctor will closely observe your numbers. Having a second abnormal blood pressure reading four hours after the first may confirm your doctor's suspicion of preeclampsia. Your doctor may have you come in for additional blood pressure readings and blood and urine tests.

Tests that may be needed

If your doctor suspects preeclampsia, you may need certain tests, including:

  • Blood tests. These can determine how well your liver and kidneys are functioning and whether your blood has a normal number of platelets — the cells that help blood clot.
  • Urine analysis. A single urine sample that measures the ratio of protein to creatinine — a chemical that's always present in the urine — may be used to make the diagnosis. Urine samples taken over 24 hours can quantify how much protein is being lost in the urine, an indication of the severity of preeclampsia.
  • Fetal ultrasound. Your doctor may also recommend close monitoring of your baby's growth, typically through ultrasound. The images of your baby created during the ultrasound exam allow your doctor to estimate fetal weight and the amount of fluid in the uterus (amniotic fluid).
  • Nonstress test or biophysical profile. A nonstress test is a simple procedure that checks how your baby's heart rate reacts when your baby moves. A biophysical profile combines an ultrasound with a nonstress test to provide more information about your baby's breathing, tone, movement and the volume of amniotic fluid in your uterus.
Jul. 03, 2014

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