Advantages of the copper IUD include its ability to provide emergency contraception up to five days after unprotected sex. It is the most effective form of emergency contraception available.[25] It works by preventing fertilization or implantation; however does not affect already implanted embryos.[26] It contains no hormones, so it can be used while breastfeeding, and fertility returns quickly after removal.[27] Copper IUDs are also available in a wider range of sizes and shapes than hormonal IUDs. Disadvantages include the possibility of heavier menstrual periods and more painful cramps.[10]