What is the reason for vaginal bleeding after pregnancy with thin endometrium?

Patient's question:

First endometrium is 19mm, 12 days later, vaginal bleeding, then checked again, endometrium is 15mm

Doctor's answer:

According to the above description of the situation, vaginal bleeding after conception may lead to the possibility of miscarriage. Therefore, it is recommended to rest in bed for half a month. Currently, sexual activity is strictly prohibited. For the patient, if the gynecological condition is severe, immediate symptomatic treatment and appropriate medication should be administered. Otherwise, it may lead to a recurrence of the gynecological condition. In addition, the patient should pay attention to their diet and psychological care.