The condom is good for people concerned about sexually transmitted diseases and infections, or for those who do not want to take any medicines. Spermicidal foam or lubricant increases the effectiveness at preventing pregnancy and decreasing the transmission of STIs. It works by stopping ovulation. Disadvantages are side effects of weight gain and depression in some women, and a common inability to get pregnant up to 1 year after stopping use of Depo Provera. They act as a barrier to prevent the passage of sperm to the egg.
Advantages are that they are used only when needed.
Disadvantages are that they require a clinician to prescribe and fit them, they must be put in with jelly before sex and left in 6 hours after sex to kill all the sperm. With the cervical cap, a couple can have repeated intercourse for 48 hours without adding more jelly or changing the cervical cap. They do not prevent all STIs. They are good for people who do not want to take medicine and do not need to worry about STIs. Proper use increases effectiveness.