Normal ALT Range in Pregnancy
For a pregnant 26-year-old female, normal ALT levels should be 6-32 IU/L in the first trimester and remain at or below 40 IU/L throughout gestation, according to the European Association for the Study of the Liver (EASL). 1
Pregnancy-Specific Reference Ranges
ALT, AST, bilirubin, bile acids, and GGT should remain normal throughout pregnancy—any elevation is pathologic and requires investigation, as recommended by the American Association for the Study of Liver Diseases. 2
The upper limit of normal ALT in pregnancy (≤40 IU/L) is lower than or similar to non-pregnant reference ranges, which typically range from 31-55 U/L for women in the general population. 3, 1
In healthy pregnancy, most liver tests remain normal, with the notable exception of alkaline phosphatase, which increases 2-fold above normal beginning in the second trimester due to placental production. 1, 2
Clinical Significance of ALT Elevation
Any ALT elevation above 40 IU/L warrants investigation for pregnancy-specific liver diseases or underlying hepatic pathology. 1
Differential Diagnosis by Degree of Elevation:
Mild elevation (up to 3-4× ULN, or ~120-160 IU/L): Most commonly intrahepatic cholestasis of pregnancy (ICP), which shows ALT elevations of 2-30 times the upper limit of normal. 1, 4
Moderate elevation (300-1,000 U/L): Suggests acute fatty liver of pregnancy (AFLP), a life-threatening condition requiring intensive care. 1, 2
Variable elevation with other features: May indicate HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) or preeclampsia with severe features. 1, 2
Mild elevation in early pregnancy with hyperemesis gravidarum: Rarely exceeds 1,000 IU/L and typically improves with hydration. 2, 4
Monitoring Approach
Baseline measurement of ALT, AST, bilirubin, and bile acids should be obtained when liver disease is suspected. 1
Serial monitoring every 2-3 weeks before 32 weeks gestation, then weekly until delivery is recommended for conditions like ICP. 1
Postpartum follow-up is essential to ensure ALT normalizes within 3 months of delivery; persistent elevation requires investigation for underlying chronic liver disease. 1, 2
Important Clinical Context
Recent research demonstrates that 13.2% of pregnant individuals presenting to labor and delivery had elevated ALT ≥25 IU/L, with 46.6% of these cases not having had liver tests checked during routine pregnancy care. 5
Elevated unexplained ALT in early pregnancy (>95th percentile, approximately >19 IU/L in non-obese women) is associated with increased risk of subsequent gestational diabetes and preeclampsia in late pregnancy. 6, 7
Critical Pitfalls to Avoid
Do not assume normal alkaline phosphatase rules out liver disease, as alkaline phosphatase physiologically increases to 133-418 IU/L in normal third trimester. 4
Do not diagnose ICP based on pruritus alone without elevated bile acids (>10 μmol/L), as this leads to unnecessary preterm deliveries. 4
Do not use obeticholic acid in pregnancy, as it lacks safety data. 4