Definition

Obstetric ultrasound uses sound waves to produce pictures of a baby (embryo or fetus) within a pregnant woman, as well as the mother's uterus and ovaries. It does not use ionizing radiation, has no known harmful effects, and is the preferred method for monitoring pregnant women and their unborn babies. A Doppler ultrasound study – a technique that evaluates blood flow in the umbilical cord, fetus or placenta – may be part of this exam.

This procedure requires no special preparation.

Obstetrical ultrasound is a useful clinical test to

establish the presence of a living embryo/fetusA
estimate the age of the pregnancy
diagnose congenital abnormalities of the fetus
evaluate the position of the fetus
evaluate the position of the placenta
determine if there are multiple pregnancies
determine the amount of amniotic fluid around the baby
check for opening or shortening of the cervix
assess fetal growth
assess fetal well-being
Some physicians also use 3-D ultrasound to image the fetus and determine if it is developing normally

Benefits

Most ultrasound scanning is noninvasive (no needles or injections).
Occasionally, an ultrasound exam may be temporarily uncomfortable, but it should not be painful.
Ultrasound is widely available, easy-to-use and less expensive than other imaging methods.
Ultrasound imaging is extremely safe and does not use any ionizing radiation.
Ultrasound scanning gives a clear picture of soft tissues that do not show up well on x-ray images.
Ultrasound is the preferred imaging modality for the diagnosis and monitoring of pregnant women and their unborn babies.
Ultrasound has been used to evaluate pregnancy for nearly four decades and there has been no evidence of harm to the patient, embryo or fetus. Nevertheless, ultrasound should be performed only when medically indicated.
Ultrasound allows the doctor to see inside the uterus and provides much information about the pregnancy.
Risks

For standard diagnostic ultrasound, there are no known harmful effects on humans.

Equipment Used

A small amount of gel is put on the skin to allow the sound waves to travel from the transducer to the examined area within the body and then back again. Ultrasound is an excellent modality for some areas of the body while other areas, especially air-filled lungs, are poorly suited for ultrasound.