Creatinine increases in amniotic fluid over gestation due to the increased fetal muscle mass. The results correlate with gestational age but not necessarily with fetal lung maturity.


Specimen: Amniotic fluid, protected from light


Testing: Chemically, as for serum.



• > 2 mg/dL: indicates 40+ weeks of gestation



• requires a certain level of renal function to provide creatinine excretion

• small for gestation fetuses have less muscle mass and so may give low values

• high maternal creatinine from renal disease can diffuse into the amniotic fluid


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