It is also normal to have a blood test for pregnancy on the 18th day of ovulation because there is a certain amount of false negative results with the use of early pregnancy test paper, while a blood test for pregnancy is a more accurate method. If a woman ovulates for 18 days, if she has intercourse during the ovulation period, a fertilized egg may be formed, and after the fertilized egg is formed, it will settle in the uterine cavity of the woman and the pregnancy will begin. Generally speaking, women will have menstruation about 14 days after ovulation. If there is still no menstruation about 14 days after ovulation, it is possible that pregnancy has occurred, but the level of human chorionic gonadotropin in the urine is still very low at this time because of the recent conception, so when using the early pregnancy test, the hormone level cannot make the early pregnancy test react, so there may be a false negative result. The result may be a false negative. However, the level of human chorionic gonadotropin in the blood test is relatively accurate, so it is easier to detect pregnancy and the result of the blood test should prevail. In case of pregnancy on the 18th day of ovulation, it is recommended to recheck the level of human chorionic gonadotropin in the blood after one week for further clarification, if it is still positive and the level of this hormone increases on top of the original one, it is basically confirmed as pregnancy.