Blood Tests for Preeclampsia

Topic Overview

A woman who may have signs of early or mild preeclampsia will have her blood tested to detect additional signs of preeclampsia. A woman who has preeclampsia may have specific blood tests to help assess her health.

• Uric acid. Increased uric acid in the blood is often the earliest laboratory finding related to preeclampsia. Uric acid is a waste product formed from the breakdown of some protein-rich foods and the breakdown of cells in the body. It is normally filtered from the blood by the kidneys. But if the kidneys have been damaged by preeclampsia, uric acid levels in the blood may rise.
• Hematocrit. A high hematocrit value can be a sign of preeclampsia. Hematocrit tells the percentage of red blood cells in the blood-a hematocrit value of 42 means that red blood cells make up 42% of the blood volume. A normal hematocrit value for a nonpregnant woman is between 36% and 44%. During pregnancy, the hematocrit value normally decreases-the fluid in the blood (plasma) increases, making red blood cells less concentrated. But preeclampsia often causes the body's tissues to absorb blood plasma. The blood becomes more concentrated, resulting in an abnormally high hematocrit value.
• Platelets. The number of platelets in the blood may be measured. Preeclampsia may cause an abnormally low platelet count.
• Partial thromboplastin time (PTT). This is a measure of the time it takes blood to clot. Preeclampsia can cause problems with blood clotting that increase the partial thromboplastin time.
• Electrolytes. Examples of important electrolytes include sodium, potassium, magnesium, calcium, and chloride. The amounts of electrolytes in the body may change if preeclampsia is causing kidney damage or is causing fluid to leak out of blood vessels into surrounding tissues (edema).
• Kidney function tests. These tests check the amount of certain substances found in the blood that are normally removed from the body by the kidneys. These substances, which include blood urea nitrogen and creatinine, increase in the blood if the kidneys have been damaged. (For more information, see the topic Creatinine and Creatinine Clearance.)
• Liver function tests. These tests monitor enzymes that indicate how well the liver is working.