Pregnancy cannot be detected by vaginal ultrasound at 30 days because it takes some time for the fertilized egg to be transported through the fallopian tube to the uterine cavity, to settle in the endometrium and develop into a gestational sac, and to show the size of the sac, as well as the fetal bud, yolk sac, and fetal heart on ultrasound images. Although vaginal ultrasound can show this significantly earlier than abdominal ultrasound, it also takes some time to develop. Therefore, for people with regular menstrual cycles, it takes at least 40-45 days of pregnancy for vaginal ultrasound to reveal visible pregnancy tissue and to be able to clarify early pregnancy. For people with irregular menstrual cycles, the gestational sac may not be visible on vaginal ultrasound even if the number of days of menopause is 40 or 45 days or more, so it takes about 45 days for early pregnancy to be visible on vaginal ultrasound.