Ultrasound during pregnancy

What is ultrasound?

Ultrasound technology uses sound waves to create a visual image (sonogram) of your baby, placenta, and uterus during pregnancy. It gives your healthcare provider valuable information about your pregnancy and your baby's health.

During an ultrasound, a technician (sonographer) uses a handheld instrument called a transducer to send sound waves through your uterus. These waves bounce off the inside of your body and your baby, and a computer translates the echoing sounds into video images that reveal your baby's shape, size, position, and movements.

When do you get your first ultrasound?

More and more doctors have ultrasound equipment in their office and are doing ultrasounds for their patients during the first trimester – as early as 6 to 10 weeks. When you call your healthcare provider to schedule your first prenatal appointment, ask whether you'll be having an ultrasound. Your provider may want you to have an early ultrasound if you've had a previous pregnancy complication, such as a miscarriage or ectopic pregnancy.

In the early stages of pregnancy, you may have a transvaginal ultrasound, which uses a wand-shaped transducer that's put in your vagina. Transvaginal ultrasound can provide better images in early pregnancy compared to a transabdominal ultrasound (which uses a transducer on the outside of your abdomen).

Transvaginal ultrasound also makes it easier to diagnose early pregnancy problems, such as a miscarriage or a molar or ectopic pregnancy.

Not all women have a first-trimester ultrasound. It's standard to have just one ultrasound during pregnancy – a mid-pregnancy transabdominal ultrasound between 18 and 22 weeks. This is sometimes called an anatomy ultrasound, because it evaluates your baby's anatomy. You can also find out your baby's sex at the mid-pregnancy ultrasound if you want (and if you haven't already found out from NIPT or another prenatal test).

What happens during a pregnancy ultrasound?

During a transvaginal ultrasound:

1. You'll empty your bladder and undress from the waist down (or wear a hospital gown).
2. You'll lie on your back with your feet in stirrups (like you do for a pelvic exam).
3. The sonographer will insert a wand-shaped transducer into your vagina. The transducer is covered with a latex sheath and is lubricated. The pressure of the wand may feel uncomfortable, but it shouldn't be painful.
4. The transducer transmits sound waves, and a computer translates the resulting echoes into pictures on a video monitor, making your baby appear on the screen before your eyes. Bone is white, fluid is black, and soft-tissue organs appear as shades of gray.
5. The sonographer records pertinent information and takes pictures or video for your provider to interpret. You can watch the process on the screen, if you like. Your provider will discuss the results with you.

During a transabdominal ultrasound:

1. You'll lie on your back on an examination table with your abdomen exposed. (Note: Come with a full bladder. This helps push your uterus up out of the pelvis and makes the images clearer.)
2. An assistant will put gel over your belly to help the sound waves move more easily.
3. The sonographer slides the transducer (the handheld device, which is about the size of a bar of soap) back and forth over your stomach. The transducer transmits sound waves, and a computer translates the resulting echoes into pictures on a video monitor, making your baby appear on the screen before your eyes. Bone is white, fluid is black, and soft tissue organs appear as shades of gray.
4. The sonographer will record your baby's measurements and take still pictures or video for your provider to interpret. You can watch the process on the screen, if you like. Your provider will discuss the results with you. Ask whether you can get pictures to take home, either printed out or on a disc.

Why do I need a pregnancy ultrasound?

Ultrasound allows your provider to check your baby's health and development, monitor your pregnancy, and look for any physical abnormalities.

First-trimester ultrasound:

If you have an ultrasound in the first trimester, it's usually too early to get a good look at your fetus's organs and limbs. But your provider can:

• Confirm that your pregnancy is in your uterus (not an ectopic pregnancy)
• Confirm your dating. How far along are you? What's your due date?
• Confirm the number of babies you're carrying (one baby, twins, or multiples)
• Help screen for certain genetic disorders
• Identify any problems with your placenta, uterus, or ovaries
• Confirm viability by seeing the heartbeat. You're likely to see your baby's heart beating if you're at least 6 weeks pregnant.

Second-trimester ultrasound:

A second-trimester (mid-pregnancy) ultrasound allows your provider to:

• Tell you for certain whether you're carrying one baby or multiples
• Check your baby's heartbeat, position, and movement
• Measure your baby's size
• Check the location of your placenta
• Check your cervical length
• Assess the amount of amniotic fluid in your uterus
• Check your baby for physical abnormalities
• Try to determine your baby's sex

Third-trimester ultrasound:

A third-trimester ultrasound allows your provider to:

• Check on your baby's growth
• Check your amniotic fluid level
• Check on your baby's well-being
• Learn whether you may need a c-section, perhaps if your baby is especially large or in breech position
• Determine the cause of vaginal bleeding, if you're having any

How long does an ultrasound take?

Ultrasounds vary in length, depending on the purpose of the ultrasound and how quickly and clearly images are available on the screen. In general, a transvaginal or transabdominal ultrasound takes between five and 20 minutes.

A mid-pregnancy (anatomy) ultrasound takes longer – about 20 to 45 minutes – because the sonographer will look closely at your baby's basic anatomy, including the head, brain, face, neck, chest, heart, spine, stomach, kidneys, bladder, arms, legs, and umbilical cord so your provider can make sure they're developing properly.

If you've had worrisome results from other ultrasounds, or if there's any other cause for concern, the sonographer will do a more thorough (level II) scan to check even more details of your baby's body. This can take anywhere from 45 to 90 minutes or more.

How many ultrasounds will I have during pregnancy?

You may have only one ultrasound (your mid-pregnancy ultrasound at 18 to 22 weeks). Or you could have several ultrasounds, for example:

• An early ultrasound in your first trimester
• A late ultrasound in your third trimester, perhaps as part of a biophysical profile
• Additional ultrasounds if there are signs of a problem with your baby or if your provider has concerns that ultrasound will help address.
• More frequent ultrasounds if you have diabetes, hypertension, or other medical complications.
• Ultrasound as part of a genetic test, such as the nuchal translucency test (NT scan), chorionic villus sampling, or amniocentesis

Are ultrasounds safe?

Yes. Numerous large studies done over the last 35 years have found no evidence that ultrasounds harm developing babies, or that there's a cumulative effect from having multiple scans. (Ultrasounds don't involve radiation, like X-rays do.).

At the same time, experts caution against unnecessary ultrasounds, pointing out that while there are no known negative effects to date, ultrasounds are a form of energy, and it's conceivable that they affect a developing baby. This may be especially true during the first trimester, when the embryo or fetus is more vulnerable to external factors.

Some centers (often found in malls and private offices) sell packages of 3D ultrasounds and 4D ultrasounds as keepsakes. While it can be tempting to get realistic photos and videos of your baby in a non-medical setting, experts recommend against it. There's no guarantee that staff at these clinics are trained properly – or that the ultrasound operator will be qualified to help you if you have questions, or if your ultrasound reveals a problem.

What if a pregnancy ultrasound shows a problem?

If problems are suspected in your pregnancy, or there's something concerning in your ultrasound results, you may be referred for a more detailed ultrasound that will be interpreted by a radiologist or maternal-fetal medicine specialist (MFM).

Often, a follow-up test shows that a suspicious ultrasound was no cause for concern.

In the unlikely event that your baby has a health problem, information from your ultrasound can help you and your provider determine how to give your baby the best outcome possible.

For example, serious heart rhythm problems can be treated with medication while a baby is still in the womb. Other abnormalities, such as a urinary tract blockage, can be treated with surgery even before birth. And knowing about any birth defects can help your provider deliver your baby safely and determine what care your baby will need right after birth.

If your baby has a dire health problem, being informed allows you to consider all the options, whether that means making the difficult decision to terminate a pregnancy, intervene medically, or prepare for the birth of a baby who needs special care.

There are people who can help you navigate the results of a concerning ultrasound. A genetic counselor can help answer a lot of your questions and guide you through your decision-making process. Many high-risk pregnancy providers can refer you to a social worker for guidance, too.

Learn more:

Prenatal tests: An overview

12 steps to a healthy pregnancy