Ultrasound can not observe the gestational sac, can not carry out medication abortion. The B ultrasound can not observe the gestational sac, there are two common situations: 1, that is, the pregnant woman has been pregnant, but the gestational sac is too small, so the uterine cavity did not see the obvious gestational sac, at this time can not be ruled out ectopic pregnancy, you should wait for a period of time before making a decision; 2, if the gestational sac is not in the uterine cavity, but in the fallopian tubes, the abdominal cavity, the ovary and other parts of the body, the occurrence of ectopic pregnancy, such a situation can not be practiced medication abortion. The following are some of the reasons for this: 1.