Estriol concentrations in blood during pregnancy.

Abstract Total plasma estriol concentrations and 24 hour total urinary estrogen excretions were measured at frequent intervals during the last half of gestation in a group of selected subjects. The blood analyses frequently gave a more reliable indication of well-being of the infant in utero than the urine analyses and was less inconvenient to the subject. Plasma estriol determination is not substantially more difficult or costly than accurate measurement of the hormone in urine, and the blood analysis therefore should replace the older method.