Between nausea, cravings or the constant need to pee, you know something’s going on inside. But pregnancy sometimes doesn’t feel entirely real until you have your first peek of your baby during your first prenatal ultrasound. Fortunately for the curious and anxious alike, pregnancy ultrasounds are a very standard — and very welcome — part of prenatal care. 

What is an ultrasound?

An ultrasound is a type of technology that uses sound waves to create images. During pregnancy, a transducer (or wand) is placed in your vagina or on top of your belly. It emits sound waves that bounce off of your baby’s tissues, fluids and bones. 

The transducer then picks up these echos and translates them into the image of your baby that you see on the screen. 

Early in pregnancy, ultrasounds are used to confirm the fetal heartbeat and the baby’s position in your uterus. Later, ultrasounds screen for fetal growth and placenta location, as well as a baby's general health and anatomy. 

Toward the end of pregnancy, ultrasounds can be useful for checking the length of your cervix (if there is any suspicion that you may be in preterm labor) as well as verifying that your baby is in a heads-down position before labor.

Who an ultrasound during pregnancy is for

All pregnant women should receive at least one ultrasound during pregnancy. 

When an ultrasound during pregnancy is done

The American College of Obstetricians and Gynecologists (ACOG) says that women should get at least one sonogram in the second trimester, between weeks 18 and 22 of pregnancy. You may also receive an additional ultrasound in the first trimester, before your 14th week of pregnancy. 

Exactly when you get your first ultrasound exam may vary, however, if you have certain chronic conditions including asthma or obesity.

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First-trimester ultrasound

An early ultrasound is often a routine part of prenatal care between 6 and 9 weeks of pregnancy, though it can happen anytime before week 14. But a first-trimester ultrasound isn’t standard practice because it’s still too early for your practitioner to see your baby in detail. 

Most practitioners wait until at least 6 weeks to perform the first pregnancy ultrasound. However, a gestational sac can be seen as early as 4 1/2 weeks after your last period, and a fetal heartbeat can be detected at 5 to 6 weeks (though that isn’t always the case).

If your doctor does decide to perform an early ultrasound, it gives you a welcome first glance of your baby. This sneak peak is used to:

 

Second-trimester ultrasound

Midway through your pregnancy, between week 18 and week 22, a trained sonographer will perform a detailed anatomy scan called a level 2 ultrasound. 

The second-trimester ultrasound is reassuring and fun to watch. It also offers you and your practitioner a picture of the overall health of your baby and your pregnancy by:

  • Measuring your baby’s size and checking all major organs
  • Estimating the amount of amniotic fluid in your uterus to make sure the level is normal 
  • Verifying the position of the placenta
  • Telling you your baby's sex (if you want to know)
  • Giving you a sneak peek at your baby (Ask the sonographer to point out your baby's hands, feet and face!) 

Routine second trimester ultrasounds are usually done in 2D. Most practitioners reserve the more detailed 3D and 4D ultrasounds for when they’re medically necessary to more closely examine a fetus for a suspected anomaly.

 While ultrasound technology is considered very safe, practitioners prefer to be extra cautious and minimize intrusions into your womb.

Additional ultrasounds during pregnancy

There are several reasons you may have additional ultrasounds during your pregnancy, including if:

  • You have any spotting during pregnancy, to confirm that all is well
  • You’re carrying multiples, to monitor their growth
  • You’re at risk of preterm labor, to check for changes in the cervix
  • Your practitioner wants to check whether your baby may be too large to deliver vaginally (for example, you have a very small pelvis or your practitioner suspects your baby is very large due to gestational diabetes)
  • Your practitioner wants to verify if your baby is in a heads-down position before birth

Additionally, ultrasounds are a part of several other pregnancy tests, including:

Doctors sometimes recommend a fetal echocardiogram, or a detailed ultrasound of a baby’s heart that’s performed by a trained technician and analyzed by a pediatric cardiologist. Your practitioner may suggest an echocardiogram if you have certain risk factors, including:

  • You have a family history of congenital heart defects 
  • Your baby’s been diagnosed with a genetic condition (like Down syndrome) 
  • You had abnormal results during another pregnancy test
  • You have certain health conditions (like diabetes or an autoimmune disease) 
  • Your baby has an abnormal heart rhythm or rate
  • You had certain infections during pregnancy, including rubella or CMV

How to prepare for pregnancy ultrasound

Wondering how to prepare for a pregnancy ultrasound? If you’re getting a transabdominal ultrasound, you should arrive at your appointment with a full bladder. This makes it easier for your doctor or sonographer to see around or through your bladder.

To time it right, some practitioners suggest emptying your bladder about 90 minutes before your exam. Then drink an 8-ounce beverage of your choice (water, juice and milk are all fine) about an hour before your appointment.

Eating about an hour before your appoinment — especially something sugary — will also get your baby moving around. This can help the sonographer take better pictures. 

Otherwise, there are no other specific preparations required for a pregnancy ultrasound. Your job: Sit back and enjoy the show! 

What to expect during first pregnancy ultrasound

There are two main types of ultrasounds used during pregnancy: transvaginal and transabdominal ultrasounds. Both types of scans typically last about 20 minutes and are painless. The type of ultrasound you’ll get depends how far along you are in your pregnancy. 

During your first ultrasound, you'll be able to watch along with your practitioner (though you'll probably need help understanding what you're seeing). You’ll likely even take home a small printout as a souvenir.

Transvaginal ultrasound

If you're getting your first pregnancy ultrasound before week 6 or 7, your practitioner will likely perform a transvaginal ultrasound. A small, long transducer (or wand) is wrapped in a sterile condom-like cover and inserted into the vagina. 

The practitioner will then move the wand within the vaginal cavity to scan your uterus. You’ll feel pressure, but it should be painless.

The transducer emits sound waves, which bounce off of structures (otherwise known as your baby) to produce an image you can see on a computer or video screen. 

Transabdominal ultrasound

If your first ultrasound is after week 6 or 7, you'll likely get a transabdominal ultrasound. Gel is rubbed onto your belly to help the sound waves move more easily. Then the wand is rubbed over your stomach to produce images of your baby.

This exam shouldn’t hurt, although it can be somewhat uncomfortable if the sonographer needs to press hard on your abdomen to see a particular part of your baby more clearly (especially with a full bladder).

The difference between sonogram and ultrasound

Though the words sonogram and ultrasound are often used interchangeably, there is a distinction:

  • Ultrasound is the term for an imaging test that uses sound to produce pictures.
  • Sonogram is the picture produced by ultrasound technology.

Risks of ultrasounds during pregnancy

Ultrasounds are noninvasive and very low-risk when performed by your health care practitioner. There is no rule on how many ultrasounds are safe during pregnancy, but ACOG recommends sticking to just one to two ultrasounds in total (outside of other circumstances where more are medically necessary).  

That said, medical guidelines caution against unnecessary exposure to ultrasound. Because no researcher would willingly put a fetus in harm's way in the name of science, it's difficult to study the long-term effects of ultrasound use — which means there is the possibility of unintended consequences with overuse. 

What's more, though ultrasounds are usually relatively accurate at estimating a baby's size, they can underestimate or overestimate weight, especially if they're overused. This may occasionally result in unnecessary C-sections or premature deliveries. 

That's why ACOG along with the Food & Drug Administration (FDA) urge practitioners and patients to only use ultrasounds if they're medically necessary. These groups also recommend that pregnant women avoid keepsake 3D and 4D sonograms during pregnancy advertised by private companies along with at-home fetal monitors. 

Some research has found that the average number of ultrasounds women are having is much higher than recommended — more than five over the course of pregnancy. So if your doctor recommends more than two ultrasounds when you're expecting, don’t hesitate to ask questions to ensure that the extra ultrasounds are medically required.