Cerclage pessary containing progesterone homogeneously distributed in the pessary body providing a prolonged, sustained and continuous release for a period of at least 6 months, wherein the pessary consists of dimethylsiloxane elastomer with RTV (Room Temperature Vulcanization) mechanism, the progesterone amount is from 20% to 30% w/w, relative to pessary weight and the ratios of the polymers forming the matrix is from 6:1 to 14 1. The cerclage pessary is useful for the prevention of preterm birth. Progesterone diffuses through the polymer continuously, without altering the shape and integrity of the pessary, since the elastomer forming the polymeric matrix used herein is not biodegradable. This guarantees that the form of pessary remains intact until the end of treatment
