The case-series of the Institute of Obstetrics and Gynaecology were examined to evaluate the suitability of urinary estriol, total plasma estriol, unconjugated plasma estriol, unconjugated plasma estetrol, plasma placental lactogen, plasma S.P.-1 glycoprotein, plasma alphafetoprotein and biparietal diameter in correctly forecasting the perinatal risk, when performed after the 25th week of pregnancy. In high-risk pregnancies, according to our results, S.P.-1 glycoprotein and urinary estriol are the most sensitive tests, while S.P.-1 glycoprotein, placental lactogen and biparietal diameter are found to have the highest predictive value. The repetition of the considered tests increases their sensitivity, but not their predictive value. In pregnancy mass screening the most suitable tests, on the basis of the "relative risk" are S.P.-1 glycoprotein (or even placental lactogen), estriol and biparietal diameter. For the last one a single measurement seems to be enough during the third trimester.