The present invention relates to novel intrauterine systems and to methods for manufacturing these systems. An intrauterine system according to the invention comprises a reservoir and a continuous, closed and flexible frame. The frame comprises a thermoplastic polyurethane elastomer made of a polycarbonate diol, 1,6-hexamethylenediisocyanate, and a chain extender.本發明係關於新穎子宮內系統且係關於製造此等系統之方法。根據本發明之子宮內系統包含貯器及連續、閉合且可撓性的框架。該框架包含由聚碳酸酯二醇、1,6-六亞甲基二異氰酸酯及鏈伸長劑製成之熱塑性聚胺基甲酸酯彈性體。