Serum unconjugated estriol levels in the third trimester and their relationship to gestational age. II.

The purpose of this study was to further validate a preliminary report concerning the clinical usefulness of serum unconjugated estriols as a marker of gestational age. Serial estriol values from 50 women with uncertain dates were plotted on semilogarithmic graphs and the gestational age predicted from the timing of the abrupt surge in estriol values which normally occurs between 35 and 36 weeks. The gestational age at birth, as determined by careful neonatal examination, agreed with the age predicted by the estriol surge within +/- 1 week.