If a woman has sex within 24 hours of ovulation, the sperm and egg will unite in the fallopian tube. Each time a man can ejaculate a large number of sperm, but eventually only one sperm will successfully enter the egg and become a fertilized egg. The egg usually survives for about one day and the sperm usually survives for about one to three days, so if you have intercourse during ovulation, even if it is not on the day of ovulation, the sperm can survive for a few days when it has already reached the fallopian tube, and as soon as the egg is released, there is a good chance that it will unite and conceive. In addition, if a woman’s fallopian tube is blocked, it is difficult for sperm and eggs to combine and for sperm to reach the fallopian tube, thus affecting pregnancy. If the fallopian tube is open but not smooth, some of the sperm and eggs will not move to the uterine cavity after combining, thus causing ectopic pregnancy. In short, sperm can reach the fallopian tube soon after sex, but whether or not pregnancy is possible is also closely related to the woman’s physical condition, such as problems with the fallopian tube, sex hormones, thyroid function, emotional stress, etc. If there are problems with the above, it is difficult to conceive even if sperm reaches the fallopian tube.