Ultrasound is not similar to X-rays or other radiation techniques, so no absorbed radiation dose will apply to the human body. It is essentially just a sound wave.
Diagnostic Ultrasound has been widely used in clinical medicine for a few decades with no proven ill effects on the human body or foetuses (unborn babies). However, if used imprudently, diagnostic ultrasound is capable of causing harmful effects.
Diagnostic Ultrasound examinations should only be performed by competent personnel who are trained and updated in safety matters. It is also important that ultrasound devices are appropriately maintained.
Ultrasound produces heating, pressure changes and mechanical disturbances in tissue. Diagnostic levels of ultrasound can produce temperature rises that are hazardous to sensitive organs and the embryo/foetus. The biological effect of non-thermal origin have been reported in animals, but to date, no such effects have been demonstrated in humans, except when a microbubble contrast agent is present.