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Estriol Secretion by the Human Term Placenta

Department of Obstetrics and Gynecology, Western Reserve University School of Medicine Cleveland, Ohio

"Free" (solvent-extractable) and "conjugated" (acid-hydrolyzable) estriol levels and their sum as total estriol were determined in paired samples of intervillous space and maternal arm vein plasma and in paired samples of umbilical artery and vein plasma. Estriol levels were determined by the method of Roy and Brown. Free and total estriol levels in the intervillous space plasma were significantly higher than those found in the maternal arm vein plasma. This suggests the transfer of estriol from the placenta to the mother and might alone account for the high urinary estriol levels found in pregnancy. No differences between free, conjugated or total estriol values were found in paired umbilical artery and vein plasma samples.

This work was supported in part by Grant AM 05739–02 from the USPHS, and by a Public Health Service Training Grant, 2G-974 DBTC(1), from the General Medical Sciences Division, USPHS.

Received June 12, 1963.

Accepted September 16, 1963.