If a woman is pregnant, it is not possible to find out exactly on which day she became pregnant, but the time of pregnancy is usually based on the size of the gestational sac or the diameter of the top of the buttocks of the fetus, and so on. For women with regular menstrual cycles, ovulation usually occurs about 14 days before the next period. It is possible to get pregnant if you have intercourse three days before and three days after ovulation. Moreover, ovarian ovulation is also affected by many factors, such as emotional factors and sexual life, which may lead to early or delayed ovulation. In medicine, pregnancy is usually calculated from the first day of the last menstrual period, which is only an approximate time, and it is not certain on which day the pregnancy occurs. If your period is irregular, you can calculate the time of pregnancy based on the size of the gestational sac or the diameter of the top of the baby’s buttocks in the early stages of pregnancy. This is an approximation and will not be accurate. After intercourse, the sperm can survive in the woman’s body for about 72 hours, during which time pregnancy can occur if ovulation occurs. After ovulation, the egg can survive in the body for about 48 hours, and you can get pregnant if you have intercourse within these 48 hours, so you can’t find out exactly what day you got pregnant.