A cervical dilator assembly features a captive extraction element in the form of a collar press-fitted over one end of an insertion element made of the self-swelling vegetable stalk laminaria japonica. A withdrawal cord is affixed to the collar, the collar being captively retained in the swollen condition of the inserted dilator element so that pull on the cord causes withdrawal of the inserted dilator element without rupture or tearing thereof. In the preferred form of the invention the collar is fabricated in the form of a migration-limiting disc.