Frank Behrens wrote that the Zierscheiben must be amulets which were worn along with other kinds of amulets including crystals, snail shells, keys, bear teeth etc all dangling in the pelvic and thigh area. Therefore they may have specifically been intended to protect the female genital area.
Ibn Fadlan wrote that when approaching a funeral pyre a Germanic pagan would cover his arse with his hand to prevent a spirit from entering him. If malicious beings can enter the body through an orifice, then naturally a woman would seek to use magical protection around her vagina.