Estriol-3-Glucuronide and Estriol-16-Glucuronide in Amniotic Fluid during Normal Pregnancy*

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Abstract
Estriol-3-glucuronide (E3-3G) and estriol-16-glucuronide (E3-I6G) have been measured in 180 samples of amniotic fluid. From the statistical analysis of the data the following conclusions were drawn. 1) For both steroids, the results had a log-normal distribution, whatever the gestational age. 2) The variance, calculated on a log basis, remained homogeneous throughout pregnancy. 3) The increase of the mean concentration of E3-3G could be expressed by a single exponential equation, but that of E3-I6G had a different pattern and could not be represented by such a simple equation. At midpregnancy E3-3G and E3-I6G were present in the amniotic fluid in similar mean concentrations (5 ng⁄ml at the 16th week). That concentration increased as pregnancy progressed and reached a mean of 300 ng⁄ml for E3-3G and 1150 ng⁄ml for E3-I6G at 40 weeks. The E3 monoglucuronide concentration in amniotic fluid was not influenced by the sex of the fetus and was not correlated with fetal weight at birth or placental weight. In clinical practice, the determination of E3-I6G concentration in amniotic fluid could be used as an additional means of assessing fetal maturity. The following limits are suggested: 1000, mature.