The chance of getting pregnant with a condom is less than 5%, and wearing a condom during sex is safe and reliable and can prevent the spread of sexually transmitted diseases. Unintended pregnancy mostly occurs when the condom is not used throughout, or when the condom slips off, or when the condom is not removed in time after intercourse, resulting in the spillage of semen. Condoms are used incorrectly, without checking the outer packaging, and are broken before use. Condoms that have expired and are broken while in use can also lead to pregnancy. Condoms are not 100% effective, but paying more attention during or after use can ensure successful contraception in most cases. Check carefully before use, remove the condom promptly after ejaculation, and check that the semen is inside the condom on it. Wearing a condom can only be used once, not continuously, to avoid increasing the chances of pregnancy.