When a condom is worn, pregnancy usually does not occur. However, pregnancy can be caused by patients wearing condoms at the wrong time or by operating them in the wrong way. First, some patients wear condoms not at the beginning of sex, but just before orgasm. But the semen before that also contains a small amount of sperm, and these sperm may lead to pregnancy, especially during ovulation, the pregnancy rate will increase. Second, due to the process of sexual life, the action amplitude is large, resulting in the condom off, sperm shot in the vagina, may also cause pregnancy. Third, the quality of condoms is not guaranteed, some condoms are of poor quality or condoms have air leakage. In this case, the patient may also get pregnant. So it is not 100% safe to wear condoms. I hope to check carefully before wearing condoms.