Diagnostic ultrasound imaging has no known risks or long-term side effects. Discomfort to the patient is very rare if the sonogram is accurately performed by using appropriate frequencies and intensity ranges. However, the application of the ALARA principle is always recommended.
There are reports of low birth weight of babies after applying more than the recommended ultrasound examinations during pregnancy. Women who think they might be pregnant should raise this issue with the doctor before undergoing an abdominal ultrasound, to avoid any harm to the fetus in the early stages of development.
Since ultrasound is energy, sensitive tissues like the reproductive organs could possibly sustain damage if vibrated to a high degree by too intense ultrasound waves. In diagnostic ultrasonic procedures, such damage would only result from improper use of the equipment.

Possible ultrasound bioeffects:
The thermal effect is controlled by the displayed thermal index and the mechanical index indicates the risk of cavitation.
An ultrasound gel is applied to obtain better contact between the transducer and the skin. This has the consistency of thick mineral oil and is not associated with skin irritation or allergy.
Specific conditions for which ultrasound may be selected as a treatment may be attached with higher risks.

See also Ultrasound Imaging Procedures, Fetal Ultrasound and Obstetric and Gynecologic Ultrasound.

Sonography [aka: ultrasonography] is a term that encompasses the entire process of performing ultrasound examinations and interpreting the obtained images.
Sonography involves the skilled application of ultrasound technology by trained professionals known as sonographers or ultrasound technologists. These specialists operate the ultrasound equipment, manipulate the transducer, and acquire the necessary pictures for diagnostic imaging purposes. Sonography requires in-depth knowledge of anatomy, physiology, and pathology to accurately interpret the ultrasound images and provide valuable information to the treating physician.
Sonography uses equipment that generates high frequency sound waves to produce images from muscles, soft tissues, fluid collections, and vascular structures of the human body. Obstetric sonography is commonly used during pregnancy. Sonography visualizes anatomy, function, and pathology of for example gallbladder, kidneys, pancreas, spleen, liver, uterus, ovaries, urinary bladder, eye, thyroid, breast, aorta, veins and arteries in the extremities, carotid arteries in the neck, as well as the heart.
A typical medical ultrasound machine, usually a real-time scanner, operates in the frequency range of 2 to 13 megahertz.

See also Musculoskeletal and Joint Ultrasound, Pediatric Ultrasound, Cerebrovascular Ultrasonography and Contrast Enhanced Ultrasound.

(TVS) The transvaginal sonography (transvaginal echography or endovaginal ultrasound), uses a small vaginal transducer (5-7.5 MHz) that is inserted into the vagina to depict the inner female organs (uterus, ovaries, vessels). As a general rule, ultrasound works better when the probe is close to the area being examined. Compared with a sonogram through the abdominal wall, the transvaginal technique produces a sharper image, not only because of the close proximity to the uterus, but also because the better signal to noise ratio of the used transducer.

Indications:

The advantage of transvaginal sonography is being able to get very close to the structures of the pelvis, and thus get better images and a more reliable diagnosis.

See also Pelvic Ultrasound, Hysterosalpingo Contrast Sonography.

Ultrasonography is another term[aka: sonography] used to describe the practice of using ultrasound technology for diagnostic imaging. It is synonymous with sonography and signifies the process of capturing ultrasound images, regardless of the body part or condition being examined. Ultrasonography is widely utilized in various medical imaging specialties, including obstetrics and gynecology, cardiology, radiology, urology, and many others. It has proven to be particularly valuable in obstetric imaging, allowing healthcare providers to monitor the growth and development of a fetus during pregnancy.
Ultrasonography uses the reflections of high-frequency sound waves to construct an image of a body organ. These ultrasonic waves are generated by a quartz crystal and are reflected at the interface between different tissues. The transmission and reflection of these high-frequency waves are displayed with different types of ultrasound modes.
See also sonogram, sonography, ultrasound imaging.