The size of the gestational sac on the ultrasound report generally has three values, namely, length, width and height, and the presence of two values is usually due to the fact that the gestational sac is too small in the early stages of pregnancy to give a third value. The gestational sac is the original placental tissue, is the initial form of pregnancy, at this time the fetus has not yet formed, fetal buds appear already have fetal heartbeat. The gestational sac can be seen on ultrasound at 5 to 6 weeks of pregnancy, and there are usually three values of the gestational sac at the time of the examination, representing the length, width, and height of the gestational sac, and usually only the long diameter is looked at. When the pregnant woman in early pregnancy to do the examination, the pregnancy sac test results only two values, may be due to the incomplete development of the fetus at this time, in order to avoid errors, only the plane measurement. Specific test results should go to the hospital to find a professional doctor to check and follow the doctor’s advice.