Elevated liver enzyme readings during pregnancy require careful investigation to determine the underlying cause. Abnormal liver function tests occur in about 3% of pregnancies and can be caused by conditions unique to gestation or those unrelated to it. While not always indicative of severe pathology, abnormal results necessitate a prompt medical assessment that accounts for the unique physiological changes of pregnancy.
What Liver Enzymes Are and Why They Matter
Liver enzymes are proteins released into the bloodstream when liver cells are damaged or bile flow is impaired. The primary enzymes signaling liver cell injury are Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST). When liver cells are injured by inflammation or disease, these transaminases spill out, causing elevated levels in blood tests.
A third enzyme, Alkaline Phosphatase (ALP), is also measured, but its interpretation differs in pregnancy. ALP levels commonly increase significantly throughout normal pregnancy due to placental production, sometimes rising up to fourfold above the non-pregnant limit. Therefore, a rise in ALP alone is usually a normal physiological change, but any increase in ALT or AST levels requires investigation.
Common and Transient Causes of Enzyme Elevation
Some elevated liver enzymes during pregnancy are due to transient causes not related to severe liver disease. Hyperemesis Gravidarum (HG), characterized by severe vomiting, is a common first-trimester cause. The resulting dehydration and metabolic stress can lead to mild elevations of AST and ALT, often two- to threefold above the normal range.
These derangements are typically self-limiting and resolve once the vomiting is managed with hydration and antiemetics. Certain medications or pre-existing conditions, such as gallstone disease, can also cause transient enzyme spikes. In many cases, the cause of elevated liver enzymes remains unclear, accounting for up to 30–40% of cases.
Elevated Enzymes Caused by Hypertensive Disorders (Preeclampsia and HELLP)
Hypertensive disorders of pregnancy are a significant cause of elevated liver enzymes, primarily Preeclampsia and its severe variant, HELLP syndrome. Preeclampsia is a multisystem disorder typically diagnosed after 20 weeks of gestation, defined by new hypertension and signs of organ damage, which can include elevated liver enzymes. Liver involvement results from endothelial dysfunction, which causes reduced blood flow to the liver and subsequent cellular ischemia.
HELLP syndrome (Hemolysis, Elevated Liver enzymes, and Low Platelet count) is a life-threatening complication of preeclampsia, though it can sometimes occur without high blood pressure. The enzyme elevations in HELLP are much higher than in isolated preeclampsia, often reaching 300 to 500 IU/L, which can be up to 30 times the upper limit of normal. These high levels reflect significant liver damage caused by microvascular injury and fibrin deposition within the liver’s blood vessels.
Symptoms accompanying this severe elevation include persistent headache, visual changes, and intense pain in the upper right abdomen or chest. This pain is often due to the liver swelling and stretching its capsule, and in rare, severe cases, it can herald a life-threatening hepatic rupture. HELLP syndrome most commonly develops between 27 and 37 weeks of pregnancy but can also occur postpartum.
Intrahepatic Cholestasis of Pregnancy
Intrahepatic Cholestasis of Pregnancy (ICP) is a liver disorder caused by impaired bile flow, leading to a buildup of bile acids in the bloodstream. This condition is the most common pregnancy-specific liver disorder, typically presenting in the late second or third trimester. The hallmark symptom is intense, generalized itching, or pruritus, which is often most severe on the palms of the hands and soles of the feet.
While ICP is diagnosed primarily by the presence of itching and elevated serum bile acid levels, liver enzymes like ALT and AST are often elevated as well. The defining biochemical feature is the high concentration of bile acids, though enzyme levels can be raised up to eight times the normal limit. The primary concern with ICP is the risk to the fetus, as high maternal bile acid levels are associated with adverse outcomes, including preterm birth and stillbirth.
Management focuses on reducing bile acid levels and alleviating maternal itching, primarily through the use of a medication called ursodeoxycholic acid. Due to the increased risk of sudden fetal demise, close monitoring of the baby and careful planning for delivery, often by inducing labor once the baby’s lungs have matured, are standard practice.
Confirming the Diagnosis and Monitoring
When elevated liver enzymes are detected, the healthcare provider initiates a systematic diagnostic pathway. This begins with a detailed review of the patient’s symptoms, trimester, and medical history. Initial laboratory work involves sequential blood tests to track ALT, AST, and ALP trends, along with checks for platelet count and bilirubin.
Specific additional tests, such as serum bile acid levels, confirm Intrahepatic Cholestasis of Pregnancy. If a hypertensive disorder is suspected, blood pressure monitoring and checks for protein in the urine are performed to confirm Preeclampsia or HELLP syndrome. Imaging, typically an ultrasound of the liver and biliary system, may also be used to rule out other causes, such as gallstones or pre-existing liver disease.
Once a pregnancy-specific liver disorder is identified, continuous monitoring of both the mother and the fetus is instituted. Maternal surveillance involves frequent blood tests and symptom checks. Fetal well-being is assessed through non-stress tests and biophysical profiles. The timing of delivery becomes a central part of the management plan, as delivery is the definitive treatment for severe conditions like HELLP syndrome and a primary intervention for managing fetal risk in ICP.