[The concentration of serum unconjugated estradiol, estriol and estetrol in pregnant women, and the significance of these hormones in pregnancy (author's transl)].

Simultaneous determinations of unconjugated estradiol (E2), estriol (E3) and 15 alpha-hydroxyestriol (E4) levels in maternal serum were studied serially to ascertain the significance of these estrogens in the feto-placental unit. The samples of serum were collected serially from 25 normal and 44 abnormal pregnancies. In normal pregnancy, these estrogen levels increased throughout pregnancy, especially E3 and E4 nearing the term. In 15 cases of IUGR pregnancy (including 4 cases of perinatal death), E2 levels were mostly low (less than M -- S.D.), E3 was within normal limits (M +/- S.D.) or low, and E4 was either high (greater than M + S.D.) or relatively low, and normal. In 9 cases of twin pregnancy, most E2 levels were within normal limits, while E3 and E4 were remarkedly high. The results signified that E2 indicated placental function, that E3 indicated placental and fetal function, and that E4 indicated fetal function.