If you are pregnant for more than 3 months, you can have an ultrasound without holding your urine. After 3 months, the uterus has enlarged significantly and you can see the baby clearly without a full bladder. However, if you want to see the low lying placenta, and the thickness of the scar, you still need to hold your urine, because the location of the placenta and the location of the scar, and the bladder is relatively close to the bladder, after the bladder is filled, you can see more clearly. In addition to ultrasound in early pregnancy, there are many also do not need to hold urine, because you can do vaginal ultrasound, vaginal ultrasound to empty the bladder to do, and vaginal ultrasound, will be more clear than the transabdominal ultrasound.