&NA;Study was made of the potential clinical utility of a random urine estrogen/creatine (E/C) ratio as an index of fetal welfare. Detailed analysis of estriol, total estrogen, and creatinine measurements as determined on biweekly 24‐hour and paired random urine samples in 20 pregnant subjects during the last 20 weeks of pregnancy was carried out. Results revealed that total urinary estrogen excretion bore a relatively constant relationship to estriol excretion, that 24‐hour creatinine excretion remained quite constant, and that values of E/C ratio in the 24‐hour urine and the paired random urine demonstrated excellent correlation. It was possible to predict the 24‐hour urine E/C ratio from the paired random urine E/C ratio to within less than ±5 with 95% confidence. A proposed practical approach to the use of the random urine E/C ratio as an index of fetal welfare is presented.