The main reasons for this are as follows: firstly, if the follicle is there but has not reached the advantage of the case if intercourse, then in the clinical survival time of sperm is 3 days, if the sperm has not ovulated within the period of survival, then this intercourse will not result in pregnancy; secondly, if there is a follicle in the same room, even if the follicle has reached the advantage of the case, if the tubes are not open, it is impossible to get pregnant; thirdly, if there is immune infertility in the case of tubal openness, then it is also possible not to get pregnant, because the cause of non-pregnancy is immunological infertility. Thirdly, if the fallopian tube is open and the follicle is dominant in the case of immune infertility, then there is also a possibility of not getting pregnant, because the cause of non-pregnancy is immune infertility, so the ultrasound found that there is a follicle, then there is a chance of getting pregnant in the coitus, but it does not necessarily achieve 100% of the purpose of pregnancy.