Birth control: IUD

What it is: There are two: the Mirena, a small T-shaped IUD, and the copper wire IUD.
How it works: The Mirena releases a hormone that thins the lining of the uterus and thickens cervical mucus, while the copper IUD makes the uterus inhospitable to sperm.
Effectiveness: The Mirena is 99.9%; the copper wire is 99.2%.
Convenience: Once it’s inserted, you don’t have to think about birth control for at least five years.
Best for: Women who cannot take estrogen and want a “semi-permanent” form of contraception.
Side effects: The copper IUD can cause heavier, more painful periods.
Price tag: The copper IUD is about $100, and the Mirena is about $350.
Good to know: A common misconception is that an IUD can “disappear” in your body but, if inserted properly, it stays put until removed by your doctor.

Our experts:
Dara Maker, family physician at Women’s College Hospital in Toronto
Roey Malleson, clinical associate professor of family practice at University of British Columbia
Ronald Weiss, assistant professor of medicine at University of Ottawa