Pregnancy should be detected 11 days after ovulation, either by a urine pregnancy test or by a blood chorionic gonadotropin test. This is because the fertilized egg will be able to implant about a week after ovulation. After the fertilized egg implants, the patient’s blood levels of various hormones such as chorionic gonadotropin, progesterone, estrogen and prolactin will rise rapidly. When the hormone levels in the blood rise, the concentration of HCG in the urine will also rise after 2-3 days. Therefore, 11 days after ovulation, both blood HCG and urine HCG levels will be very high, so pregnancy can be detected and the urine test should be strongly positive. However, pregnancy may not be detected by ultrasound after 11 days of ovulation because the fertilized egg is still relatively small at this time, and even if a gestational sac is formed, it is still very small and cannot be detected by ultrasound, or if an ultrasound is done, a relatively small gestational sac-like echo of about 0.2-0.3 cm may be seen, but if it is too small, intrauterine pregnancy cannot be confirmed and needs to be observed.