After sex, the time for the sperm in male semen to reach the uterine cavity from the vagina is related to sperm vitality and whether the woman has gynecological inflammation. After sex, sperm usually enter the uterine cavity in 0.5-1.5 hours and the fallopian tube in about 2-6 hours. If ovulation has already occurred at this time, the egg can unite with sperm in the fallopian tube to form a fertilized egg, which takes 6-7 days to enter the uterine cavity for implantation. If ovulation has not yet occurred, the sperm will wait for the egg in the fallopian tube. Once the ovary ovulates, the umbilical end of the fallopian tube can catch the egg into the fallopian tube and unite with the sperm to form a fertilized egg. If the sperm cannot unite with the egg, it will gradually die within 24-36 hours. In addition, intercourse during ovulation can increase the chances of pregnancy. If your period stops for more than 1-2 weeks, you can use an early pregnancy test or gynecological ultrasound to determine if you are pregnant. During pregnancy preparation, both men and women need to take folic acid supplements in advance to prevent fetal neural tube abnormalities.