Abstract
An investigation has been carried out to assess the accuracy by which the diurnal urinary excretion of oestriol (dU-oestriol) in pregnant women can be estimated from urine specimens collected in periods less than 24 hours. Night urines (9 h) are not recommended as a substitute for diurnal urines (24 h). Even correlation of the oestriol output from the night urines with the output of creatininium gives day by day variations which are significantly greater than the corresponding variations of the diurnal urines. in cases where the collection of a correct diurnal urine specimen (24 h) is difficult to obtain and it is important to get a quick answer it is recommended to use a single voided urine specimen and to calculate the diurnal excretion of oestriol by means of the creatininium output.