A device for retarding birth including an upper ring for surrounding a cervix, an anchoring component for anchoring the device, and an elastic component for attaching the upper ring to the anchoring component, wherein the elastic component pushes the upper ring and the anchoring component apart. A device for retarding birth including a sleeve for surrounding a cervix along a greater portion of a length of the cervix, a support strip on the sleeve directed along an axis of the sleeve, and a ring at least partially around the sleeve, in which when a top of the sleeve is pushed to expand radially, the support strip pivots on the ring, such that an end of the support strip near the top of the sleeve moves radially outward, and an end of the support strip near the bottom of the sleeve moves radially inward. Related apparatus and methods are also described.
