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Harvard Health Publications

Fetal Ultrasound

What is the test?



How do I prepare for the test?

Early in the pregnancy, you may be asked to drink several glasses of water an hour before the ultrasound so that the uterus can be seen more clearly (a full bladder moves the intestines out of the way). Later in the pregnancy, the uterus has grown sufficiently in size so that this is not necessary.

What happens when the test is performed?

You lie on your back on a table for the test. A technician or doctor first squirts some clear jelly onto your lower abdomen to help the ultrasound sensor slide around easily, and then places the sensor against your skin. The sensor looks like a microphone. When the sensor is in place, a picture appears on a TV screen, and the technician or doctor moves the sensor back and forth on your abdomen to see the fetus from many different views. Depending on the age of the fetus, the heartbeat, movement of arms and legs, and many of the internal organs may be seen.

What risks are there from the test?

There are no risks to either the mother or the fetus from ultrasound.

Must I do anything special after the test is over?

The jelly is wiped off. There are no side effects from the test.


Depending on whether the person doing the test is a doctor or a technician, you might be able to get a few results of your test immediately. You may even be given a printed picture of your baby as seen by ultrasound, to take home. The test is recorded on a videotape; a radiologist can review the tape and report to your doctor, a process that might take a day or two.
