Staying up late does not directly cause infertility, because infertility is mostly caused by diseases of the reproductive system, such as abnormal fallopian tubes and ovulation disorders in women, and sperm production disorders and sexual dysfunction in men. However, staying up late for a long time may affect female ovulation and male sperm quality, reducing the chances of pregnancy. If both spouses stay up late occasionally for special reasons such as work and life, there is generally no significant impact on the body and no harm to the reproductive system. If both spouses stay up late often, women may affect the regulation of their own biological clocks, affecting the normal metabolism of the body, which leads to endocrine disruption and affects the normal menstrual cycle. When the menstrual cycle is disrupted, it is difficult to accurately determine when a woman is ovulating, which may reduce the chances of pregnancy. Men staying up late for a long time may lead to a decrease in sperm vitality, resulting in lower fertilization ability, or even after pregnancy, the embryo is in a poor quality state and there may be a risk of pre-eclampsia miscarriage. For women, factors affecting infertility mainly include fallopian tube abnormalities, such as congenital malformation and narrowing of the fallopian tubes, and ovulation disorders. In men, the main causes of infertility are testicular dysplasia, orchitis and other reproductive disorders, or sperm production disorders due to endocrine disorders, and sexual dysfunction, resulting in the inability of sperm to unite with the egg. In summary, staying up late usually does not directly cause infertility, but may reduce the chances of pregnancy. It is recommended that both men and women adjust their physical condition, allocate their time reasonably and reduce the number of late nights before choosing to become pregnant.