Ultrasound is a type of imaging. It uses high-frequency sound waves to look at organs and structures inside the body. Health care professionals use it to view the heart, blood vessels, kidneys, liver, and other organs. During pregnancy, doctors use ultrasound to view the fetus.

HSN which is also called sonohysterogram, is a new minimally invasive technique that involves the slow infusion of sterile saline into a woman’s uterus during ultrasound imaging. HSN allows the doctor to evaluate abnormal growths inside the uterus, abnormalities of the tissue lining the uterus (the endometrium): or disorders affecting the deeper tissue layers. HSN does not require radiation or contrast media, or invasive surgical procedures.

It can be used for the evaluation of the following patients:

Peri or postmenopausal women with unexplained bleeding
Women whose endometrium appears abnormal during baseline ultrasound imaging
Women with fertility problems, infertility is sometimes related to polyps, leiomyomas (fibroids), or adhesions inside the uterus. Adhesions are areas of tissue that have grown together to form bands or membranes across the inside of the uterus.
HSN is useful as a screening test to minimize the use of more invasive diagnostic procedures, such as tissue biopsies and dilatation and curettage (D&C). It can also be used as a follow up after uterine surgery to evaluate its success.

The precautions include:

Difficult to perform in clients with certain abnormalities
Cervical stenosis, i.e. the lower end of the uterus is narrowed or tightened. It complicates the inserstion of the tube (catheter)
Adhesions or large fibroids: Can sometimes block the flow of saline fluid into the uterus.
Clients with active PID (Pelvic Inflammatory disease) should not be tested with HSN until the disease is brought under control. Women with chronic PID or heart problems are given antibiotics before the procedure.

A pelvic ultrasound scan is the most effective imaging modality used to examine the uterus and ovaries. It is may also be used during pregnancy to monitor the health and development of the embryo or fetus. The scan can either be transabdominal or transvaginal.

Obstetric ultrasonography is the use of medical ultrasonography in pregnancy, in which sound waves are used to create real-time visual images of the developing embryo or fetus in its mother's uterus (womb).

Early pregnancy monitoring begins when a woman has a positive home pregnancy test confirming that she is pregnant. Following this, serum quantitative HCG assays should be performed twice a week. These measure the blood levels of the pregnancy hormone, human chorionic gonadotropin. This is followed by weekly ultrasound scans over the next 8 – 12 weeks.