Stem pesaries, c 1930.
© Science Museum / Science & Society Picture Library
Stem pesaries are intra-uterine devices (IUDs) consisting of a rubber, metal, or glas stem attached to a cup or button to hold the stem upright and prevent it from becoming lost in the uterus. An IUD works after conception by denying a newly fertilized embryo the ability to implant and grow in the lining of the uterus. The IUD is the most inexpensive long-term reversible method of contraception available. Smaller, plastic IUDs are still used today.