An ultrasound is necessary to determine if the abortion is clean. Because ultrasound can directly see the shape of the uterine cavity, and whether there is any residual tissue inside the uterus. Medical abortion is to make the uterus contract and the embryonic tissues flow out by taking medicine, which is preferred by many women because of the relatively small damage to the uterus. However, some women still have residual tissue after a medical abortion, and some even need to undergo removal surgery. After the medication abortion, if you see the embryonic tissue discharged on the day of the medication abortion, generally two weeks later, go to the hospital for follow-up, do ultrasound examination without any abnormality, indicating that the abortion is clean. If the embryonic tissue is not discharged on the same day of the medical abortion, usually go to the hospital one week later to do ultrasound review. Review ultrasound found in the uterine cavity has uneven echo, to consider that there are residual not completely clean flow.