If the egg is fertilized, the blastocyst will be formed through division, and it will start to implant on the 5th-6th day, and the implantation will be successful on the 7th day, so the chorionic gonadotropin in the blood will be elevated on the 7th day after the fertilization. If you can determine the time of ovulation, you can determine the time of implantation. If you want to check whether you are pregnant or not, you can do a blood test on the seventh day after ovulation, and if the chorionic gonadotropin in the blood doubles in 48 hours or less, it mostly indicates that the pregnancy is relatively normal. If the doubling is not good, it is possible that the pregnancy is biochemical or ectopic, and further dynamic observation should be carried out.