Comparison between Serum Levels of Oestriol in Venous and Capillary Blood from Pregnant Women

Abstract

During pregnancy, estriol is formed by the placenta mainly from fetal precursors. Measurements of estriol excretion in urine or estriol concentration in blood are widely used for assessment of the fetoplacental function. This study was undertaken to determine the relationship between the concentration of estriol in venous and in capillary blood from pregnant women, and to decide whether the more practical method of finger-prick capillary blood sampling could replace venous blood sampling for estriol estimations in the management of high-risk pregnancies. Forty-one pregnant women with gestational ages ranging from 30 to 40 weeks volunteered for the study (Table 1). An excellent correlation was found between venous and capillary samples for unconjugated estriol (r = 0.92, P < 0.001). The correlation was the same for samples from women with uncomplicated pregnancies as for samples from women with complicated pregnancies. When the mean relative difference between the venous and capillary values of unconjugated estriol was calculated for samples from women with complicated pregnancies, no difference was observed. For samples from women with uncomplicated pregnancies, the values were slightly higher in the venous blood. In Table 2, the clinical information obtained from the estriol measurements of venous and capillary blood is compared. The information disagreed in only one of 78 samples. The day-to-day variability for unconjugated estriol was of the same order in the venous as in the capillary samples. Total estriol was measured in 28 samples. The correlation between values obtained in venous and in capillary blood was 0.78 (P < 0.05).