Does LDH Increase with Pregnancy?
Yes, lactate dehydrogenase (LDH) levels can increase during pregnancy, particularly in the third trimester and especially in pathological conditions like preeclampsia, HELLP syndrome, and acute fatty liver of pregnancy (AFLP).
Normal Pregnancy Changes
In uncomplicated pregnancy, LDH levels show variable patterns:
- Third trimester elevation: Platelet LDH activity is significantly increased in the last trimester of normal pregnancy 1
- Isoenzyme shifts: LDH-1 isoenzyme increases during late pregnancy and at term, though total serum LDH may remain unchanged in normal pregnancy 2
- The baseline range remains relatively stable, with mean levels around 378.6 ± 124 IU/L in normotensive pregnant women 3
Pathological Elevations - Critical Clinical Context
The most clinically significant LDH elevations occur in pregnancy-related complications, where LDH serves as both a diagnostic marker and severity indicator:
HELLP Syndrome and Preeclampsia
LDH elevation is a defining feature of these conditions 4:
- Mild preeclampsia: Mean LDH 302.9 ± 138.5 IU/L (or 580.5 ± 213 IU/L in another cohort) 3, 5
- Severe preeclampsia: Mean LDH 488.6 ± 223.4 IU/L (or 932.2 ± 448 IU/L) 3, 5
- Eclampsia: Mean LDH 1515.86 ± 754 IU/L 3
The mechanism involves endothelial damage causing microangiopathic hemolytic anemia and hepatic ischemia from fibrin deposition in hepatic sinusoids 4.
Acute Fatty Liver of Pregnancy (AFLP)
Elevated LDH is a key diagnostic criterion in AFLP 4. The Swansea criteria for AFLP diagnosis include elevated transaminases and other markers, with LDH elevation helping differentiate AFLP from preeclampsia when combined with prolonged PT, reduced fibrinogen, and other laboratory abnormalities.
Clinical Significance and Risk Stratification
LDH levels correlate directly with disease severity and adverse outcomes:
- LDH > 800 IU/L: Significantly increased maternal complications including placental abruption, HELLP syndrome, DIC, acute renal failure, and maternal death 3
- LDH 600-800 IU/L: Intermediate risk for complications 3
- LDH < 600 IU/L: Lower complication rates 3
Fetal/Neonatal Outcomes
Higher maternal LDH levels correlate with:
- Preterm delivery
- Intrauterine growth restriction (IUGR)
- Low APGAR scores (< 7 at 1 and 5 minutes)
- Increased NICU admissions
- Intrauterine fetal death 3, 5
Important Clinical Caveats
Common pitfall: Interpreting mildly elevated LDH in isolation without clinical context. LDH elevation in pregnancy must be evaluated alongside blood pressure, proteinuria, platelet count, liver enzymes, and coagulation studies to distinguish normal physiological changes from pathological conditions.
Key distinction: While normal pregnancy may show modest LDH increases (particularly platelet-derived), dramatic elevations signal serious pregnancy complications requiring urgent intervention and delivery after maternal stabilization 4.