How to Prepare for an Obstetrical Ultrasound
You should wear a loose-fitting, two-piece outfit for the examination. Only the lower abdominal area needs to be exposed during this procedure.
If an ultrasound is ordered by your doctor early in your pregnancy, you may be told to have a full bladder for the procedure. Air interferes with sound waves, so if your bladder is full, the air-filled bowel is pushed out of the way by the bladder, making it easier to get an image of the uterus and embryo or fetus.
For early pregnancies, the radiologist or sonographer may want to use a transvaginal ultrasound. This requires an empty urinary bladder. You should ask for specific instructions for this imaging study when you make your appointment.