Lactate dehydrogenase (LDH) is an enzyme found throughout the body, playing a role in cellular energy production. When cells are damaged, LDH can leak into the bloodstream. In pregnancy, measuring LDH levels provides important insights into maternal health.
What LDH Is and Its Role in Pregnancy
Lactate dehydrogenase (LDH) is an enzyme present in nearly all tissues and organs, including the liver, kidneys, heart, muscles, and red blood cells. Its primary function involves converting lactate to pyruvate, essential for energy production. Normally, LDH levels in the blood are low because the enzyme remains within cells. When cells are damaged, LDH is released into the bloodstream, making it a general indicator of tissue injury. In pregnancy, monitoring LDH levels helps identify potential issues affecting organs like the liver or indicating red blood cell breakdown (hemolysis).
Defining Normal and Elevated LDH Levels
Normal LDH levels vary by laboratory and individual physiological state. For non-pregnant adults, a typical reference range is 115-211 units per liter (U/L). During pregnancy, LDH levels naturally increase as gestation progresses. Ranges might be 78-433 U/L in the first trimester, 80-447 U/L in the second, and 82-524 U/L in the third trimester. Some research indicates LDH levels up to 600 U/L can be observed in normal pregnancies.
An elevated LDH level in pregnancy is considered above these typical ranges. Levels exceeding 400 U/L are associated with hypertension and preeclampsia. Levels greater than 600 U/L are linked to preeclampsia and eclampsia. Severe preeclampsia can involve mean LDH levels around 556 U/L, and levels over 800 U/L are seen in a percentage of severe cases.
Conditions Associated with High LDH
Elevated LDH levels in pregnancy indicate medical conditions requiring immediate attention. Preeclampsia and HELLP syndrome are the most prominent, posing risks to both the pregnant individual and the baby. High LDH levels suggest cellular damage or dysfunction, particularly affecting the liver or red blood cells.
Preeclampsia
Preeclampsia is characterized by high blood pressure and damage to organ systems, often the liver and kidneys. Elevated LDH reflects liver cell injury or red blood cell breakdown (hemolysis). Higher LDH levels correlate with increased preeclampsia severity and greater maternal and fetal complications. LDH is a useful marker for monitoring disease progression and potential adverse outcomes.
HELLP syndrome
HELLP syndrome is a complication often considered a variant of preeclampsia. HELLP stands for Hemolysis (red blood cell breakdown), Elevated Liver enzymes, and Low Platelet count. High LDH levels are a key diagnostic criterion for hemolysis in HELLP syndrome, indicating red blood cells are being destroyed.
Interpreting Results and Next Steps
An elevated LDH level during pregnancy is not a standalone diagnosis but one piece of a larger clinical picture. If a high LDH reading is found, healthcare providers conduct further evaluations. These include reviewing symptoms, blood pressure, and additional laboratory tests like liver function tests and platelet counts.
Interpretation of LDH results occurs within the context of the individual’s overall health and pregnancy circumstances. Additional tests help determine the underlying cause and guide management. A comprehensive assessment by a healthcare professional is important for accurate diagnosis and to determine necessary next steps.