A role for estriol in human labor, term and preterm.

Although estriol has been studied as an indicator of fetal well-being in the past, its broader biologic role has not been elucidated. Estriol in the maternal compartment closely reflects fetal adrenal activity, and increased fetal adrenal activity prior to the onset of labor is a common link in mammalian parturition. In humans, estriol increases before spontaneous labor and may be a clinically useful marker for some cases of preterm labor.