Contraception is used to prevent pregnancy. Some methods use hormones. The combined pill contains oestrogen and progesterone. Taken every day, it keeps these hormones high, so the pituitary releases less FSH, eggs do not mature and there is no ovulation. Progesterone also thickens the cervical mucus, which makes it hard for sperm to get through. The implant and injection release progesterone slowly, and the patch releases hormones through the skin, so they last longer than a daily pill.
Other methods are non-hormonal. Barrier methods, such as the condom and the diaphragm, stop sperm reaching the egg. Condoms also protect against sexually transmitted infections (STIs). An intrauterine device (IUD) is placed in the uterus and stops sperm surviving or an embryo implanting. Sterilisation permanently stops eggs or sperm meeting. Abstinence avoids sex altogether.
To evaluate methods, compare how effective they are and what the drawbacks are. Hormonal methods are more than 99% effective when used correctly, but the pill fails more often in everyday use if doses are forgotten, so the implant is more effective in everyday use. Hormonal methods can cause side effects and do not protect against STIs. Condoms are slightly less effective at preventing pregnancy but protect against STIs. People also weigh up cost and ethical or religious views.