Uric Acid
Uric Acid — Trimester-Specific Reference Ranges
Serum uric acid decreases early in pregnancy due to hemodilution and increased renal clearance, then gradually rises in late pregnancy. Elevated uric acid is commonly associated with hypertensive disorders of pregnancy.
| Units | Nonpregnant | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| mg/dL | 2.5 – 5.6 | 2.0 – 4.2 | 2.4 – 4.9 | 3.1 – 6.3 |
| µmol/L | 149 – 333 | 119 – 250 | 143 – 292 | 184 – 375 |
Physiologic changes in pregnancy
- Early ↓ due to increased renal clearance and plasma volume expansion
- Gradual ↑ in late pregnancy due to increased fetal production and maternal catabolism
- Marked elevations raise concern for preeclampsia or renal disease
Causes of low uric acid
- Pregnancy (physiologic in early gestation)
- SIADH
- Fanconi syndrome
- Low protein intake / malnutrition
- Liver disease
- Medications (allopurinol, uricosurics)
Causes of high uric acid
- Preeclampsia / gestational hypertension
- Renal insufficiency
- Dehydration
- High cell turnover (hemolysis, malignancy)
- Metabolic syndrome / insulin resistance
- Lead toxicity
- Medications (diuretics)
References
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table. Obstet Gynecol. 2009;114:1326–31. PMID: 19935037
- Williams Obstetrics, 26th ed. Renal physiology in pregnancy.
- Roberts JM, et al. Preeclampsia pathophysiology and biomarkers.