Generally, pregnant women only need to hold their urine during the transabdominal ultrasound examination in early pregnancy, and usually do not need to do so at other times. However, there are some special cases where you need to ask your doctor about the examination in advance so that you can be prepared. In early pregnancy, because the uterus is relatively small, a full bladder is needed as a reference to determine the position of the uterus, so urine should be held. However, if a vaginal ultrasound is done, there is no need to hold your urine. As the weeks of pregnancy grow, usually after 12 weeks of pregnancy, there is usually no need to hold your urine for the ultrasound at this time as the uterus has grown and amniotic fluid is present. However, if the bladder is needed as a reference for checking the low position of the placenta, the pregnant woman should hold her urine a little for the test. In addition, some special circumstances still need to hold urine for ultrasound. For example, when a pregnant woman has back pain and needs to rule out urinary tract diseases, holding her urine can make the bladder full and help the examination; when she has lower abdominal pain and vaginal bleeding in the middle and late stages of pregnancy and needs to know the length of the uterus, holding her urine can also facilitate the relevant tests. It is important to note that it is not recommended that pregnant women hold their urine frequently during pregnancy unless necessary. Occasional holding of urine has little effect, but prolonged holding may cause the bladder to lose its elasticity, resulting in urinary incontinence, or overfilling of the bladder may compress the uterus, which may have an effect on the fetus.