Contraception lowers the chance of pregnancy. Some methods use hormones. The combined pill contains oestrogen and progesterone. These hormones inhibit the release of FSH, so no egg matures and no ovulation takes place. Progesterone also makes the mucus at the cervix thicker, so sperm cannot reach the egg. Other hormonal methods are the implant, the injection and the patch, which release hormones slowly into the blood.
Non-hormonal methods include barrier methods such as condoms and the diaphragm, which stop sperm reaching the egg. The IUD is a small device placed in the uterus. Sterilisation is a permanent operation, and abstinence means not having sex. Condoms are the only method in this list that also protect against sexually transmitted infections (STIs).
To evaluate a method, look at how effective it is and what its drawbacks are. The implant and the IUD are over 99 percent effective because the user cannot forget them. The pill is also over 99 percent effective when taken correctly, but it fails if pills are missed. Condoms are less effective in real use because they can be put on wrongly or split. Hormonal methods can cause side effects such as headaches or mood changes. People also choose methods for personal, medical or religious reasons.