In recent years, ultrasound has developed the ability to provide 3 dimensional images. For some medical and fetal problems, the use of 3D is valuable. Because of the ability to produce higher quality pictures of a fetus, many providers will offer this to patients.
The American Institute of Ultrasound in Medicine has provided an official statement about the use of 3D ultrasound. For the most part, this is something that can be provided to the patient as an incidental image in the course of a normal diagnostic test. There should be no additional charge to the patient for this keepsake image.