Ultrasound during pregnancy
Ultrasound (also called sonogram) is a prenatal test offered to most pregnant women. It uses sound waves to show a picture of your baby in the uterus (womb). Ultrasound helps your health care provider check on your baby’s health and development.
Ultrasound can be a special part of pregnancy—it’s the first time you get to “see” your baby! Depending on when it’s done and your baby’s position, you may be able to see his hands, legs and other body parts. You may be able to tell if your baby’s a boy or a girl, so be sure to tell your provider if you don’t want to know!
Most women get an ultrasound in their second trimester at 18 to 20 weeks of pregnancy. Some also get a first-trimester ultrasound (also called an early ultrasound) before 14 weeks of pregnancy. Talk to your provider about when an ultrasound is right for you.
What are some reasons for having an ultrasound?
Your provider uses ultrasound to do several things, including:
- To confirm (make sure) you’re pregnant
- To check your baby’s age and growth. This helps your provider figure out your due date.
- To check your baby’s heartbeat, muscle tone, movement and overall development
- To check to see if you’re pregnant with twins, triplets or more (also called multiples)
- To screen for birth defects, like spina bifida or heart defects. Screening means seeing if your baby is more likely than others to have a health condition; it doesn’t mean finding out for sure if your baby has the condition. After an ultrasound, your provider may want to do more tests, called diagnostic tests, to see for sure if your baby has a birth defect. Birth defects are health conditions that a baby has at birth. Birth defects change the shape or function of one or more parts of the body. They can cause problems in overall health, in how the body develops, or in how the body works.
- To help with other prenatal tests, like chorionic villus sampling
- To examine your ovaries and uterus (womb). Ovaries are where eggs are stored in your body.
- To check for pregnancy complications, including ectopic pregnancy, molar pregnancy and miscarriage.
Are there different kinds of ultrasound?
Yes. The kind you get depends on what your provider is checking for and how far along you are in pregnancy. All ultrasounds use a tool called a transducer that uses sound waves to create pictures of your baby on a computer. The most common kinds of ultrasound are:
- Transabdominal ultrasound. When you hear about ultrasound during pregnancy, it’s most likely this kind. You lay on your back on an exam table, and your provider covers your belly with a thin layer of gel. The gel helps the sound waves move more easily so you get a better picture. Then he moves the transducer across your belly. You may need to have a full bladder during the test because sound waves move more easily through liquid than through air. Ultrasound is painless, but having a full bladder may be uncomfortable. The ultrasound takes about 20 minutes.
- Transvaginal ultrasound. This kind of ultrasound is done through the vagina (birth canal). You lay on your back on an exam table with your feet in stirrups. Your provider moves a thin transducer into your vagina. You may feel some pressure from the transducer, but it shouldn’t cause pain. Your bladder needs to be empty or just partly full. This kind of ultrasound also takes about 20 minutes.
In special cases, your provider may use these kinds of ultrasound to get more information about your baby:
- Doppler ultrasound. This kind of ultrasound is used to check your baby’s blood flow if he’s not growing normally. Your provider uses a transducer to listen to your baby’s heartbeat and to measure the blood flow in the umbilical cord and in some of your baby’s blood vessels. You also may get a Doppler ultrasound if you have Rh disease. This is a blood condition that can cause serious problems for your baby if it’s not treated. Doppler ultrasound usually is used in the last trimester, but it may be done earlier.
- 3-D ultrasound. A 3-D ultrasound takes thousands of pictures at once. It makes a 3-D image that’s almost as clear as a photograph. Some providers use this kind of ultrasound to make sure your baby’s organs are growing and developing normally. You also may get a 3-D ultrasound to check for problems in the uterus.
- 4-D ultrasound. This is like a 3-D ultrasound, but it also shows your baby’s movements in a video.
Does ultrasound have any risks?
Ultrasound is safe for you and your baby when done by your health care provider. Because ultrasound uses sound waves instead of radiation, it’s safer than X-rays. Providers have used ultrasound for more than 30 years, and they have not found any dangerous risks.
If your pregnancy is healthy, ultrasound is good at ruling out problems, but not as good at finding them. It may miss some birth defects. Sometimes, a routine ultrasound may suggest that there is a birth defect when there really isn’t one. While follow-up tests often show that the baby is healthy, false alarms can cause worry for parents.
You may know of some places, like stores in a mall, that aren’t run by doctors or other medical professionals that offer “keepsake” 3-D or 4-D ultrasound pictures or videos for parents. The American College of Obstetricians and Gynecologists, the Food and Drug Administration and the American Institute of Ultrasound in Medicine do not recommend these non-medical ultrasounds. The people doing them may not have medical training and may give you wrong or even harmful information.
What happens after an ultrasound?
For most women, ultrasound shows that the baby is growing normally. If your ultrasound is normal, just be sure to keep going to your prenatal checkups.
Sometimes, ultrasound may show that you and your baby need special care. For example, if the ultrasound shows your baby has spina bifida, she may be treated in the womb before birth. If the ultrasound shows that your baby is breech (feet-down instead of head-down), your provider may try to flip your baby’s position to head-down, or you may need to have a cesarean section (also called c-section). A c-section is surgery in which your baby is born through a cut that your doctor makes in your belly and uterus.
No matter what an ultrasound shows, talk to your provider about the best care for you and your baby.
For more information
The March of Dimes has partnered with the American Institute of Ultrasound Medicine, Johns Hopkins University and Parents.com to create a unique peak into a baby’s development inside the womb. These images reveal the details of a baby’s growth from a collection of cells to a full-term newborn:
Last reviewed October 2014
Frequently Asked Questions
How is blood pressure measured?
Blood pressure is the force of blood that pushes against the walls of your arteries. Arteries are blood vessels that carry blood away from your heart to other parts of the body. If the pressure in your arteries becomes too high, you have high blood pressure. High blood pressure is also called hypertension.
At each prenantal care visit, your health care provider checks your blood pressure. To do this, she wraps an inflatable cuff around your upper arm. She pumps air into the cuff to measure the pressure in your arteries when the heart contracts (gets tight) and then relaxes.
Your blood pressure reading is given as two numbers: the top (first) number is the pressure when your heart contracts and the bottom (second) number is the pressure when your heart relaxes. A healthy blood pressure is 110/80. High blood pressure happens when the top number is 140 or greater, or when the bottom number is 90 or greater
Your blood pressure can go up or down during the day. Your provider can re-check a high reading to find out if you have high blood pressure during pregnancy.
Last reviewed March 2012
See also: High blood pressure during pregnancy, Preeclampsia, HELLP syndrome
Can a rubella shot hurt my baby during pregnancy?
If you got your rubella shot around the time you got pregnant, it's unlikely that your baby will be harmed by the vaccine. However, it's best to wait to get pregnant for 28 days after vaccination because there is a very small risk of potentially hurting the baby. To date, there hasn't been any birth defects reported that are attributed to the rubella vaccine. In any case, the risk of harming your baby by getting the vaccine at the time you got pregnant is much lower than the risk of harming your baby if you caught rubella during pregnancy.
I couldn't see my baby at my 7 week ultrasound. Why?
At the 7th week of pregnancy, your baby is about ½ an inch long or the size of a blueberry. He's very small. When a transabdominal ultrasound (done on your belly) is done at such an early stage, it's possible that the baby can't be seen. It could be because it's too early in the pregnancy or because you conceived a little later than what you thought. Your health care provider might recommend a transvaginal ultrasound (done inside the vagina) to help see the baby more clearly.
What are choroid plexus cysts?
The choroid plexus is the area of the brain that produces the fluid that surrounds the brain and spinal cord. This is not an area of the brain that involves learning or thinking. Occasionally, one or more cysts can form in the choroid plexus. These cysts are made of blood vessels and tissue. They do not cause intellectual disabilities or learning problems. Using ultrasound, a health care provider can see these cysts in about 1 in 120 pregnancies at 15 to 20 weeks gestation. Most disappear during pregnancy or within several months after birth and are no risk to the baby. They aren't a problem by themselves. But if screening tests show other signs of risk, they may indicate a possible genetic defect. In this case, testing with higher-level ultrasound and/or amniocentesis may be recommended to confirm or rule out serious problems.