Plasma progesterone, estradiol, and unconjugated estriol concentrations in twin pregnancies: Relation to cervical length and preterm delivery.

Plasma concentrations of progesterone, estradiol and unconjugated estriol at 18-24 weeks are not associated with cervical length or preterm delivery in twin pregnancies. Vaginal progesterone treatment does not increase the circulating progesterone concentration. Cervical length, but not hormone concentrations, is predictive of preterm delivery in twin gestations. This article is protected by copyright. All rights reserved.