Intrauterine device with a restricted upward movement of a string

An intrauterine device with a restricted upward movement of a plurality of strings, having an elongated central vertical stem of an order of 29 to 35 mm in length with a plurality of arms attached on a proximal end of the central vertical stem and a spherical bulge attached on a distal end of the central vertical stem, wherein the plurality of strings are terminated together on one end at the spherical bulge, and each of the plurality of strings has an opposite, unterminated end that together form a hanging portion of said plurality of strings configured to suspend freely from the spherical bulge in the vaginal cavity, and an envelope directly connected to the spherical bulge by at least covering the spherical bulge and wherein the envelope has sealed ends to prevent harboring of infection, and wherein the envelope is disposed around the hanging portion of the plurality of strings emerging from below the spherical bulge to achieve an enhanced stiffness fora projected length of the hanging portion of plurality of strings proximal to the attachment to the spherical bulge, with the hanging portion of plurality of strings extending away from the spherical bulge and beyond said envelope without retention between the envelope and the unterminated ends of the hanging portion of strings, and configured to remain inside the endocervical canal so as to restrict the upward movement of the plurality of strings in the uterus.