Contraception (birth control) prevents pregnancy by interfering with the normal process of ovulation, fertilization, and implantation. There are different kinds of birth control that act at different points in the process. Any woman who wants to prevent pregnancy must use a reliable form of birth control. Birth control (contraception) is designed to interfere with the normal process and prevent the resulting pregnancy. There are different kinds of birth control that act at different points in the process, from ovulation through fertilization to implantation. Choices for those who don't want to take a pill include contraceptive patches, vaginal rings, implants, diaphragms, birth control pills, condoms, injectables, intra-uterine devices and more permanent methods such as vasectomy. No specific preparation is needed before using contraception. An IUD (as described above) can be fitted as an emergency contraceptive method up to five days after unprotected sex or up to five days after the earliest predicted date of ovulation. It is over 99% effective at whatever stage it is fitted in the process. A trained doctor or nurse can remove it at a woman's next period if this is what she wants or she can keep it for an ongoing method of contraception. An abortion is a procedure used to end a pregnancy before it results in the birth of a baby. This can be carried out with either medical or surgical intervention. There are various reasons as to why someone may need an abortion, which can be decided after advice by a gynecologist.