Estriol and estetrol in amniotic fluid

Estetrol (1,3,5(10)-estratrien-3,15α,16α,17β-tetrol; 15α-hydroxyestriol; E 4 ) is derived from both neutral and phenolic precursors which have undergone 15α-hydroxylation in the fetal liver or adrenal. Radioimmunoassays of total estrogens (TE), unconjugated estriol (E 3 ), and unconjugated estetrol (E 4 ) have been utilized to measure the concentrations of these estrogens in 46 amniotic fluid samples from 27 high-risk patients. Thirteen normal patients, 5 diabetic patients, and 9 patients with pregnancy complicated by Rh sensitization were studied. The concentration of TE in amniotic fluid in the uncomplicated pregnancies ranged from 11 to 65 μg per 100 ml. In most cases, the concentrations of E 3 and E 4 were similar, ranging from 0.5 to 2 per cent of the TE, as is expressed by a narrow range of E 3 :E 4 ratios extending from 0.8 to 4.5, with a mean of about 3.0. TE, E 3 , and E 4 concentrations in amniotic fluid obtained from pregnancies complicated by diabetes mellitus or Rh sensitization did not differ significantly from concentrations found in uncomplicated pregnancies of the same period of gestation. TE concentrations in 33 third-trimester serum samples from 6 patients ranged from 2 to 17 μg per 100 ml. In maternal serum, the concentration of unconjugated E, is usually much higher than the concentration of unconjugated E 3 , with an E 3 :E 4 ratio of approximately 9. TE concentration in amniotic fluid is similar to or higher than TE concentration in maternal serum; E 4 concentration is also higher in amniotic fluid; E 3 concentration is lower in amniotic fluid. There is little indication from this study that the concentration of unconjugated E 4 in amniotic fluid is of predictive value for the diagnosis of fetal compromise.