Cervical Pessary Compared With Vaginal Progesterone for Preventing Early Preterm Birth: A Randomized Controlled Trial.

Objective: To compare the effectiveness of a cervical pessary and vaginal progesterone to prevent spontaneous preterm births in pregnant women with cervical lengths 25 mm or less as measured by transvaginal ultrasonography.

Methods: This was a multicenter, open-label, randomized, noninferiority trial. Women with singleton pregnancies and a short cervix (25 mm or less) measured transvaginally at the second-trimester ultrasonogram were invited to participate.