Gräfenberg's ring
(重定向自Grafenberg ring)
Gräfenberg's ring is a flexible ring of silk suture, later versions of which were wrapped in silver wire. It was an early IUD, a birth control device. Gräfenberg's ring was the first IUD used by a significant number of women. The ring was introduced by German gynecologist Ernst Gräfenberg in 1929. It ceased to be in wide use circa 1939.