Abstract
Amniotic fluid creatinine, uric acid and urea were measured by an automated method in 127 pregnancies. The concentration of each solute increased with gestational age. A creatinine concentration of 2.0 mg/100 ml could be used to pick up 52.9% of “mature” fetuses (i.e. fetuses which had passed the 37th week of gestation) but there was a false positive pick-up of 5%. A uric acid concentration of 5.0 mg/100 ml correctly indicated a mature fetus in 41.5% of patients, the false positive pick-up being 3.3%. Amniotic fluid urea was not a useful index of fetal maturity.