Abstract: An intrauterine device for preventing egg fertilization having a membrane, a frame having a first arm and a second arm, the first and second arms movable from a first position to a second more expanded position. The frame supports the membrane to move the membrane between a first position to a second more expanded position, wherein the first and second arms are non-planar and each arm has a proximal portion, an intermediate portion and a distal portion, The first arm has a bend at the intermediate portion so that the intermediate portion of the first arm lies in a different plane than the proximal portion of the first arm and the second arm has a bend at the intermediate portion so the intermediate portion of the second arm lies in a different plane than the proximal portion of the second arm. An elongated tail portion extends proximally of the membrane. The membrane can have a convex distal portion.