Ultrasound Scans

There is something quite magical about seeing your baby on a screen for the first time. But an ultrasound scan isn't just a chance to have a little peek at your baby. It's also an important medical examination, and the information it provides can be used to check your baby's development, estimate your due date, identify some physical conditions and look at things such as the position of your placenta. So what actually happens during an ultrasound scan? And what can it tell you? Let's take a look.

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What is an Ultrasound Scan?

 

An ultrasound scan uses sound waves to create an image of your baby inside the womb. The sonographer moves a small handheld device, called a probe, over your abdomen. The sound waves are used to create images that appear on a screen. Ultrasound scans are generally painless and there are currently no known risks to the pregnant person or baby from having an ultrasound scan.  Most scans are carried out by a specially trained healthcare professional called a sonographer.

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How Many Scans Will I Have?

 

In England, you'll usually be offered two routine ultrasound scans during pregnancy:

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Around 11 to 14 weeks

This is often called the dating scan or 12-week scan.

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Around 18 to 21 weeks

This is the 20-week screening scan, sometimes called the anomaly scan or mid-pregnancy scan. 

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You may be offered additional scans depending on your individual circumstances. For example, you might have extra scans to monitor your baby's growth, check the position of your baby or placenta, or monitor something identified during pregnancy. Having additional scans doesn't automatically mean that something is wrong. Your maternity team should explain why you're being offered an additional scan and what they are looking for.

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The Dating Scan

 

Your first routine scan usually takes place between around 11 and 14 weeks. It's often called the dating scan because one of its purposes is to estimate how far along your pregnancy is and calculate your estimated due date. The sonographer measures your baby and uses these measurements to estimate your baby's gestational age. The scan can also check:

• Your baby's development

• Whether your baby is growing in the womb

• Whether you're expecting more than one baby

• Whether the pregnancy is developing in the expected location 

 

Your estimated due date may be adjusted based on the ultrasound measurements. Remember, though, that your due date is still an estimate. Your baby hasn't been handed a calendar and told when to make their grand entrance. You can read more about this in [Due Dates & Gestation].

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The Dating Scan and Screening

 

The dating scan may also be part of the combined screening test for Down's syndrome, Edwards' syndrome and Patau's syndrome.

If you choose to have this screening, the scan includes a measurement called the nuchal translucency (NT), which looks at the amount of fluid at the back of your baby's neck. This measurement is combined with information from a blood test and other factors to calculate your baby's chance of having one of these conditions. The important thing to remember is that this is screening, not diagnosis. You can read more about this in: [Screening in Pregnancy] and [Understanding Screening Results].

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The 20-Week Screening Scan

 

Your second routine scan usually takes place between around 18 and 21 weeks. It's commonly called the 20-week scan, although you might also hear it called the:

• Anomaly scan

• Mid-pregnancy scan

• Fetal anomaly scan

• Detailed scan

 

This is another screening test. The scan looks in detail at your baby's physical development and screens for 11 specific physical conditions. The sonographer looks closely at areas including your baby's:

• Brain

• Face

• Heart

• Spine

• Bones

• Abdomen

• Kidneys

 

The scan also checks your baby's growth and looks at your placenta. 

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What are the 11 Conditions Screened For?

 

The 20-week screening scan looks for signs of:

• Anencephaly

• Open spina bifida

• Cleft lip and palate

• Diaphragmatic hernia

• Gastroschisis

• Exomphalos

• Serious cardiac abnormalities

• Bilateral renal agenesis

• Severe skeletal dysplasia

• Edwards' syndrome (trisomy 18)

• Patau's syndrome (trisomy 13) 

 

That list can sound quite frightening. It's worth remembering that most scans show that a baby appears to be developing as expected.

But the scan cannot detect every health condition. Some conditions are easier to see on ultrasound than others. For example, the current NHS screening information states that around 90% of babies with open spina bifida will be detected through the scan, whereas around 50% of babies with heart conditions will be detected. So a normal scan is reassuring, but it isn't a guarantee that your baby has no health conditions.

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What Actually Happens During the Scan?

 

Most ultrasound scans take place in a dimly lit room so the sonographer can see the screen clearly. You'll usually be asked to:

1. Lie on a couch.

2. Raise your top and lower your trousers or skirt enough to expose your abdomen.

3. Have some ultrasound gel applied to your tummy.

4. Have the sonographer move the ultrasound probe over your abdomen.

 

The sonographer will take measurements and carefully examine your baby. They may need to apply a little pressure with the probe to get a good view. The scan itself is usually painless, although some parts can feel a little uncomfortable, particularly if you have been asked to attend with a full bladder. A routine scan generally takes around 20 to 30 minutes, although it can take longer if it's difficult to get all the images needed. 

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What if my Baby Won't Cooperate?

 

This is very common. Your baby doesn't understand that you've booked a 20-minute appointment and the sonographer has a checklist to complete. They may be curled up in an awkward position, moving around a lot or simply refusing to provide a good view of their heart, spine or other body parts. If the sonographer can't get all the images they need, they may ask you to move around, take a short break or return for another appointment. This doesn't necessarily mean there is a problem. Sometimes your baby is simply being spectacularly unhelpful.

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Can I Bring Someone With me?

 

You can usually bring someone with you to your scan, although individual hospitals have their own policies. Most hospitals don't allow children to attend ultrasound appointments, so it's worth checking beforehand rather than turning up with your entire existing family.

And remember that an ultrasound scan is a medical examination, even though it can also be a lovely and emotional experience.

The sonographer needs to concentrate on obtaining the images and completing the examination.

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Why is the Sonographer Sometimes so quiet?

 

This is something worth knowing before you go. You may be lying there watching your baby on the screen while the sonographer is moving the probe around, measuring things and occasionally saying very little. And your brain may immediately start writing an entire disaster movie. Try not to read too much into the silence.

 

The sonographer needs to concentrate on the examination and may need to work through a series of measurements and images before they can discuss what they've seen. You can always ask: "Are you able to tell me how everything is looking?" They should explain the results of the scan to you once the examination is complete.

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Can I Find out my Baby's Sex?

 

Finding out your baby's sex isn't part of the national screening programme. Some hospitals will tell you if they are able to see it during the 20-week scan, while others have a policy of not doing so. It's also not always possible to tell. Your baby's position may make it difficult to see, and the sonographer cannot guarantee that the information will be correct. If you do want to know, check your local hospital's policy beforehand. And if you don't want to know, tell the sonographer at the beginning of the scan.

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Can I Have a Picture?

 

Many hospitals offer printed or digital ultrasound pictures, although this varies between maternity services and there may be a charge.

Check with your hospital if this is something you'd like.

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What Happens if Everything Looks Normal?

 

Most scans show that the baby appears to be developing as expected. If everything looks reassuring, you'll usually continue with your routine antenatal care. It's important to remember that ultrasound screening cannot identify every possible health condition. If you develop symptoms or have concerns about your pregnancy after a normal scan, you should still contact your maternity team. A normal scan is a snapshot of what can be seen at that particular point in pregnancy. It's not a guarantee for the rest of pregnancy.

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What if Something Unexpected is Seen?

 

Sometimes a scan identifies something unexpected. This doesn't always mean that your baby definitely has a health condition. The sonographer may need to obtain a second opinion, arrange another scan or refer you to a specialist. You may also be offered further testing to find out more about what has been seen.

 

Depending on the circumstances, this could include further ultrasound scans or diagnostic tests such as amniocentesis or chorionic villus sampling (CVS).  If this happens, you'll be given more information about what has been found, what it might mean and what your options are. You don't have to know all the answers immediately. It's okay to ask questions. It's okay to take time to understand the information.

And it's okay to ask for support.

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Do I Have to Have an Ultrasound Scan?

 

No. The routine dating and 20-week scans are offered, but you do not have to have them. Screening is your choice, and your maternity care should continue if you decide not to have a particular screening scan.  This is worth thinking about before your appointment.

 

For some people, having information about their baby's development feels reassuring and helpful. For others, the possibility of receiving unexpected information can feel more difficult. There isn't a universally "right" decision. If you're unsure, talk to your midwife about what the scan involves, what information it could provide and what might happen if something unexpected is found. You can also read [Screening in Pregnancy] for more information about making decisions around screening.

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Questions to Ask Before your Scan

 

You don't need to arrive with a list of 25 questions. But these might be useful:

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"What is this scan looking for?"

"Is this a screening scan?"

"Will I get the results on the day?"

"Do I need a full bladder?"

"Can I bring someone with me?"

"Can I bring my children?"

"Can I find out the sex of my baby?"

"What happens if you can't get all the images you need?"

"What happens if something unexpected is seen?"

And if you're feeling particularly anxious about the scan:

"Can you explain what you're checking as you go?"

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You may not get a running commentary throughout the examination because the sonographer needs to concentrate, but letting them know you're anxious can help them understand what you need.

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A Scan is a Medical Examination, not a Crystal Ball

 

It's easy to think of an ultrasound scan as a way of seeing your baby. And it can be a wonderful experience. But its primary purpose is medical. It gives your maternity team information about your baby's development and can identify some conditions or things that may need further investigation. It also has limitations. It can't see everything. It can't predict everything. And it can't guarantee what your pregnancy or birth will look like. That's why a scan can be both reassuring and uncertain at the same time.

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The Bottom Line

 

If you're offered an ultrasound scan during pregnancy, it can be helpful to understand what you're actually being offered. Ask:

 

What is this scan looking for?

What can it tell me?

What can't it tell me?

What might happen if something unexpected is found?

Do I want this information?

 

And remember: You are allowed to ask questions before you agree to screening. You don't have to understand everything immediately.

And you don't have to make a decision based on fear. Information is most useful when you understand what it means.

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Explore Next

 

[Understanding Screening Results]
Already received a screening result? Learn how to interpret the numbers, understand what "higher chance" and "lower chance" actually mean, and explore what may happen next.

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[Questions to Ask About Tests]
A practical list of questions to help you understand the tests and investigations you're offered during pregnancy.

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[Pregnancy Appointments]
Understand what happens during routine antenatal appointments and how you can make them work for you.