The way this ultrasound (or sonogram) is done is you will have a full bladder before the start of the exam. Your ultrasound technician will have you lay back on a table. Your pregnant belly will have a special gel placed on it to help enhance the picture from the sound waves of the ultrasound. The technician, or in some cases the physician, will use the ultrasound transducer wand and move it over your abdomen.
Images will appear on the screen. Some of the images will be measured and recorded. Many times you will be given some of the images to keep for fun. Some places will even let you record the session on a DVD. (This varies doctor to doctor, be sure to ask before your appointment, in case they require you to supply the DVD.)
Some of the things that they will look for will help them determine things about your baby and your pregnancy. They may look at the size of your baby in comparison to others babies of the same gestational age or they may look at your placenta.