As long as a woman is not in her menstrual period and there are no obvious symptoms of vaginal infection, it is possible to have sex during a delayed menstrual period, but most of the delayed menstrual periods are related to pregnancy. If you are pregnant, it is still not recommended to have sex in early pregnancy because the fetus is not very stable in early pregnancy and if you have sex during this period, it will easily lead to miscarriage of the fetus.