A copper intra uterine device (IUD) is the most effective way to prevent pregnancy after unprotected sex.
A copper IUD can be put in as emergency contraception, up to five days after unprotected sex — or within 5 days of your earliest expected date of ovulation.
If you want to, you can leave your copper IUD in — it’s really good long-acting contraception. The copper IUD protects you from pregnancy for 5-10 years, depending on which one you get. You can have it removed anytime you want to — plus it’s 99% effective at preventing pregnancy.