Amniotic fluid reference intervals
COMPONENT CONVENTIONAL UNITS FACTOR RECOMMENDED SI UNITS
APPEARANCE Early Gestation Term Clear Clear or slightly opalescent - - Clear Clear or slightly opalescent
ALBUMIN Early Gestation Term 0.39 g/dL 0.19 g/dL 10 3.9 g/L 1.9 g/L
BILIRUBIN Early Gestation Term <0.075 mg/dL <0.025 mg/dL 17.10 <1.3 µmol/L <0.41µmol/L
CHLORIDE Early Gestation Term Approximately equal to serum chloride Generally 1-3 mEq/L lower than serum chloride - 1 Generally 1-3 mmol/L lower than serum chloride
CREATININE Early Gestation Term 0.8 - 1.1 mg/dL 1.8 - 4.0 mg/dL (generally >2 mg/dL) 88.40 71 - 97 µmol/L 159 - 354 µmol/L (generally >177 µmol/L)
ESTRIOL Early Gestation Term <10 µg/dL <60 µg/dL 3.468 <347 nmol/L >2081 nmol/L
LECITHIN/SPHINGOMYELIN Early (Immature) Term (Mature) <1:1 >2:1 1 1 <1:1 >2:1
OSMOLALITY Early Gestation Term Approximately equal to serum osmolality 230 - 270 mOsm/kg 1 1 Approximately equal to serum osmolality 230 - 270 mmol/kg
PCO2 Early Gestation Term 33 - 55 mm Hg 42 - 55 mm Hg (increases toward term) 0.1333 4.4 - 7.3 kPa 5.6 - 7.3 kPa (increases toward term)
pH Early Gestation Term 7.12 - 7.38 6.91 - 7.43 (decreases toward term) 1 7.12 - 7.38 6.91 - 7.43
PROTEIN, TOTAL Early Gestation Term 0.60 ± 0.24 g/dL 0.26 ± 0.19 g/dL 10 60 ± 2.4 g/L 2.6 ± 1.9 g/L
SODIUM Early Gestation Term Approximately equal to serum sodium 7 - 10 mEq/L lower than serum sodium 1 7 - 10 mmol/L lower than serum sodium
CYTOLOGICSTAINING, OIL RED O Early Gestation Term NILE BLUE SULFATE Early Gestation Term <10% >50% 0 >20% 0.01 0.01 Stained fraction: <0.1 >0.5 Stained fraction: <0.0 >0.2
Urea Early Gestation Term 18.0 ± 5.9 mg/dL 30.3 ± 11.4 mg/dL 0.1665 3.00 ± 0.98 mmol/L 5.04 ± 1.90 mmol/L
URIC ACID Early Gestation Term 3.72 ± 0.96 mg/dL 9.90 ± 2.23 mg/dL 59.48 221 ± 57 µmol/L 589 ± 133 µmol/L
VOLUME Early Gestation Term 450 - 1200 mL 500 - 1400 mL (increases toward term) 0.001 0.45 - 1.2 L 0.5 - 1.4 L (increases toward term)