Between the nausea, cravings and constant need to pee, you know something’s going on in there. But pregnancy sometimes doesn’t feel entirely real until you have that first peek at your baby during your first prenatal ultrasound. Fortunately, pregnancy ultrasounds are a very standard — and very welcome — part of prenatal care.
What is an ultrasound?
An ultrasound is a type of imaging technology that uses soundwaves to create a picture, or sonogram, of structures inside your body, including your growing baby. During pregnancy, a transducer or wand is placed in your vagina or on top of your belly. The wand emits soundwaves that bounce off your baby’s tissues, fluids and bones 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 baby's general health and anatomy.
Toward the end of pregnancy, ultrasounds can be used to check the length of your cervix (especially 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 delivery.
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.[1] You may also receive an additional ultrasound in the first trimester, before your 14th week of pregnancy.
However, if you have certain chronic conditions such as asthma or obesity, the timing of your ultrasounds may vary.
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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). The gestational sac provides nourishment and eventually produces cells that turn into baby’s umbilical cord, blood cells and reproductive organs.
If your doctor decides to perform an early ultrasound, it gives you a welcome first glance of your baby. This sneak peak is used to:[2]
- Confirm your estimated due date more accurately by measuring the fetus
- Check the fetal heartbeat
- Make sure the pregnancy is in the uterus (to rule out an ectopic pregnancy, which typically happens in a fallopian tube)
- Determine whether you’re carrying multiples
Second-trimester ultrasound
Midway through your pregnancy, between weeks 18 and week 22, a level 2 ultrasound will be done to see baby’s anatomy in detail.
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 glimpse of 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.
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 cytomegalovirus (CMV)
How to prepare for pregnancy ultrasound
If your doctor orders 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 appointment — 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 are painless and typically last about 20 minutes. The type you have will depend on 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 soundwaves, which bounce off 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 (especially with a full bladder) if the sonographer needs to press hard on your abdomen to see a particular part of your baby more clearly.
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 set rule for 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, 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.
Both ACOG and the Food and Drug Administration (FDA) also recommend that pregnant women avoid keepsake 3D and 4D sonograms marketed by private companies, along with at-home fetal monitors. While the FDA says there is a lack of evidence of any harm due to ultrasound imaging and heartbeat monitors, they also note there isn’t enough research to rule out any long-term effects.
What's more, although ultrasounds are usually relatively accurate at estimating a baby's size, they can also underestimate or overestimate weight, which may occasionally result in unnecessary C-sections or premature deliveries.
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.
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