Correlation between morning urine estriol concentration and 24-hour estriol excretion

In an attempt to circumvent the need for 24-hour urine collections for estriol analyses in assessment of fetal status, the possibility of using morning urine samples was investigated. Results indicate 1) good correlation between 24-hour estriol excretion and morning estriol concentration, and between corresponding E/C ratios, 2) similar morning and 24-hour estriol concentrations, 3) high dependence of estriol and creatinine excretion on 24-hour urine volume but not on morning volume, 4) larger variations in 24-hour than in morning urine volume, and 5) better consistency of values in morning than in 24-hour samples in pathologic pregnancy. The use of serial morning urine concentrations at least as an outpatient monitoring procedure is suggested.