A prenatal ultrasound is a safe and painless test that uses sound waves to make
images that show the baby's shape and position. It can be done in the first, second,
or third trimester, depending on what the health care provider is looking for.
The American College of Obstetrics and Gynecologists (ACOG) recommends at least
one ultrasound during a pregnancy, but many women have two or more. Women with high-risk
pregnancies might have multiple ultrasounds during their pregnancy.
During an ultrasound, sound waves are bounced off the baby's bones and tissues
to make an image showing the baby's shape and position in the uterus. Also called
a sonogram, sonograph, echogram, or ultrasonogram, an ultrasound is done to:
To prepare for a prenatal ultrasound, you might be asked to drink lots of fluids
or not pee for a while so that your bladder will be full for the exam.
You'll change into a cloth gown and lie on a table. The room is usually dark so
the images can be seen clearly on the computer screen. A technician (sonographer)
trained in ultrasound imaging will spread a clear gel on your abdomen. This gel helps
with the transmission of the sound waves.
The technician will move a small wand (a transducer) over the gel. The transducer
emits high-frequency sound waves and a computer measures how the sound waves bounce
back from the body. The computer changes those sound waves into images. Sometimes
a doctor will come in at the end of the test to meet with you and take a few more
The prenatal ultrasound is painless. You may feel a slight pressure on the belly
as the transducer is moved over the body, and the gel may feel wet or cold. The test
usually takes less than 30 minutes.
Sometimes an ultrasound test can be done through the vagina (called a transvaginal
ultrasound) early in the pregnancy when the uterus and ovaries are better
seen from that angle.
Some ultrasounds can show the fetus in three dimensions, like a photograph (a 3D
ultrasound), and sometimes show movement (a 4D ultrasound).
Doctors might use these to look for birth
Should I Have a Prenatal Ultrasound?
This test is considered safe, but it's up to you whether to have it. Talk to your
health care provider to find out why and when this test is recommended for you.
When Are Prenatal Ultrasounds Done?
The timing of the test will depend on why the health provider is recommending it.
ultrasounds (also called standard or "level 2" ultrasounds) usually are done between
18–20 weeks to examine the fetal anatomy and to confirm normal development.
This test can often show the gender of the fetus (as long as the fetus is "cooperating"
and in the right position). If you want your baby's gender to be a surprise, make
sure to tell the doctor or technician at the start of this test.
can examine the placenta and the position of the fetus. Sometimes an ultrasound is
part of a test called a biophysical profile (BPP) to see whether
the fetus is getting enough oxygen. The BPP examines the baby's breathing, movement,
amount of amniotic fluid, tone, and heart rate response.
When Are the Results Available?
Although the technician can see the images immediately, a full evaluation may take
up to 1 week if a doctor or specialist is not on site during the exam.
Depending on where you have the ultrasound done, the technician may be able to
tell you that day if everything looks OK. However, most radiology centers or health
care providers prefer that technicians not comment until a specialist has taken a
look — even when everything is OK.