In most cases the pregnancy is 15 days old and the presence of the gestational sac is not visible through ultrasound. There are only a few cases where the patient’s embryo is so well developed that the presence of a relatively small gestational sac can be seen by vaginal ultrasound. On the 15th day of pregnancy, the gestational sac is about 0.3-0.5 cm, but the patient cannot be judged to have a normal intrauterine pregnancy by this examination. Because there may be the following two special cases: First, the patient’s intrauterine gestational sac is a false gestational sac, the patient’s real gestational sac has not yet appeared, and the possibility of ectopic pregnancy cannot be ruled out. Secondly, the patient may have an intrauterine pregnancy combined with an ectopic pregnancy. Therefore, the patient needs to monitor the blood progesterone and HCG levels to determine whether the pregnancy is intrauterine and whether it is a normal pregnancy.