Ultrasound is widely used in daily clinical obstetrical practice. Many medical indications exist for performing a sonographic examination but, in addition, several researchers have published information on the importance of patients watching the ultrasound monitor during the examination, particularly during three- and fourdimensional (3D/4D) scanning, for maternal-fetal bonding. Furthermore, a certain form of ultrasound, called “entertainment” or “keepsake” ultrasound has flourished, particularly in the United States. While ultrasound is assumed to be completely safe, it is a form of energy and, as such, has effects in tissues it traverses (= bioeffects). The two most important mechanisms for effects are thermal and non-thermal. Nonthermal mechanisms include cavitation, streaming, and even release of free radicals. These two major mechanisms are indicated on-screen by two indices: The thermal index (TI) and the mechanical index (MI). It is important to be aware of these effects to be able to prevent potential harm. Ultrasound machine controls can alter the instrument acoustic energy and hence the exposure but different machines behave differently. Therefore each clinician should know how this occurs in his/her own machine. Unfortunately, it appears the general knowledge in this area is poor and an effort should be made to educate the endusers. Whether 3D/4D enhances parental-fetal bonding is still a matter of discussion.