Why Serum Uric Acid Increases in Pregnancy-Induced Hypertension
Serum uric acid increases in pregnancy-induced hypertension primarily due to reduced renal clearance from decreased glomerular filtration, increased tubular reabsorption, and decreased tubular secretion caused by renal dysfunction and poor organ perfusion that characterizes hypertensive disorders of pregnancy. 1
Primary Pathophysiologic Mechanisms
Renal Dysfunction and Reduced Clearance
- The fundamental mechanism is impaired renal handling of uric acid due to the poor organ perfusion that characterizes gestational hypertension and preeclampsia 1
- Renal dysfunction leads to decreased uric acid excretion, with elevated creatinine levels often accompanying the hyperuricemia 2, 3
- The lack of normal spiral artery remodeling in the placenta creates higher vascular resistance, contributing to reduced renal perfusion 1
Increased Production from Placental Oxidative Stress
- Increased xanthine oxidase activity and oxidative stress in the placenta contribute to elevated uric acid production in preeclampsia 2
- This represents tissue breakdown and cellular damage occurring in the poorly perfused placenta 2
Clinical Significance and Diagnostic Value
Correlation with Disease Severity
- Serum uric acid levels correlate directly with the severity of pregnancy-induced hypertension, with higher levels seen in severe preeclampsia compared to mild gestational hypertension 4, 2, 3
- Mean uric acid levels in severe PIH (6.65-8.24 mg/dL) are significantly higher than mild PIH (5.42-6.14 mg/dL) and normotensive pregnancy (4.25-4.88 mg/dL) 3
- Uric acid demonstrates superior diagnostic efficiency (sensitivity 79-87%, specificity 71-84%) compared to creatinine for detecting PIH 4, 2
Monitoring Recommendations from Guidelines
- Guidelines recommend monitoring uric acid levels at 28 and 34 weeks minimum in gestational hypertension, and twice weekly in established preeclampsia 1
- Elevated maternal uric acid specifically warrants closer fetal growth monitoring, as it correlates negatively with fetal birth weight 1, 2
Important Clinical Caveats
Limitations as a Predictive Tool
- While uric acid levels are elevated in PIH, there is appreciable overlap between hypertensive and normotensive groups, making it unreliable for predicting hypertension development in individual women 5
- A rapidly rising uric acid level should prompt heightened surveillance, but the absolute level alone should not dictate delivery timing 1
- Uric acid levels do not reliably predict the severity of HELLP syndrome, despite being elevated in women with this complication 6
Practical Threshold
- Serum uric acid levels ≥5.5 mg/dL serve as a useful indicator of PIH and are associated with increased perinatal morbidity and mortality 3
- However, clinical decisions should integrate uric acid with other markers including blood pressure trends, proteinuria, platelet count, liver enzymes, and creatinine 1