20 week pregnancy ultrasound scan: here's what to expect
Pregnancy scan experts explain all you need to know about your second routine ultrasound scan: what exactly it checks for, how long it takes, when you get the results – and if you'll find out if your baby's a boy or a girl
Your 20-week ultrasound scan – sometimes called the mid-pregnancy scan or the anomaly scan – is the second of 2 routine pregnancy scans you are offered on the NHS.
As its name suggests, it usually carried out when you are about 20 weeks into your pregnancy – and it takes a really detailed look at your baby and at your womb.
But what exactly is the sonographer (who operates the ultrasound equipment) looking for? How is it different the 12-week scan you had earlier in your pregnancy? Will it take longer? What you still need to drink water lots of water beforehand? And is this the scan where you find out if you're having a boy or a girl?
Here, with the expert help of Gill Harrison, professional officer for ultrasound at the Society and College of Radiographers, is a clear, complete and concern-soothing guide to your second routine pregnancy scan...
Your 20-week pregnancy ultrasound scan: here's what to expect
What is the 20-week scan? | When will I be offered my 20-week scan? | Do I have to have a 20-week scan? | What exactly does the 20-week scan check? | Will I find out my baby's sex at the 20-week scan? | How do I prepare for my 20-week scan? | What happens at the 20-week scan? | How long will the 20-week scan take? | What will I be able to see? | Can I bring my partner to my 20-week scan? | Can I take my children to my 20-week scan? | Is the 20-week scan done in 3D? | Will I get a photo to keep? | Can I take my own photo or make a recording? | Will I find out the results straightaway? | What conditions is the 20-week scan looking for? | Will the 20-week scan find everything? | What if I have questions about my scan report? | What happens if there are signs of a problem? | Will I have any more scans after the 20-week scan?
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What is the 20-week scan for?
It's a scan to check how your baby is growing, whether your baby is developing normally for this stage of your pregnancy, and whether there are any unexpected physical conditions.
"We get a really clear picture of your baby's anatomy from this scan," says Gill. "And, because there's so much detail to see – assuming your baby isn't in an awkward position – you can get some stunning views of your baby's face and hands and feet."
When will I be offered my 20-week scan? Will it be at exactly 20 weeks?
Although it's called the 20-week scan, you won't necessarily be given an appointment for the scan at exactly 20 weeks. But it will be offered to you at round about that mark: if you're in England or Wales or Scotland, it will be offered at between 18 and 21 weeks; if you're in Northern Ireland, it will be offered at between 18 and 20 weeks.
As with your 12-week scan, your 20-week scan will usually take place in a hospital local to you, and you will receive a letter or a text confirming the date, time and place.
Do I have to have the 20-week scan? Is it safe?
Ultrasound scans use high-frequency sound waves to capture a picture of your baby inside your womb. There are no known risks, either to you or to your baby, from having a pregnancy ultrasound scan in a professional health setting, such as the NHS.¹²³
You can, however, choose not to have any pregnancy scan, if you don't want to.4
What exactly does the 20-week scan check?
This scan looks in detail at your baby's:
- Head and brain, to check size and shape. Your baby's head circumference will be measured, and their face checked for signs of a cleft lip.
- Spine, both along its length and in cross section, to make sure that all the bones align, and that skin covers the spine at the back.
- Abdominal wall, to make sure it covers all the internal organs at the front. Your baby's abdominal circumference will also be measured.
- Heart. The top two chambers (atria) and the bottom two chambers (ventricles) of your baby's heart should be equal in size. The valves should open and close with each heartbeat. Your sonographer will also examine the major veins and arteries which carry blood to and from your baby's heart.
- Stomach. Your baby swallows some of the amniotic fluid they lie in (to practise breathing). This fluid should be seen in their stomach as a black bubble.
- Kidneys. The sonographer will check that your baby has two kidneys, and that urine flows freely from them into the bladder.
- Arms, legs, hands and feet, including their fingers and toes. The length of your baby's thigh bone will also be measured.
The sonographer will also look at:
- Your placenta, the umbilical cord and the aminiotic fluid. They'll check where your placenta's lying and make sure it's developing as it should.
"Your sonographer will look specifically for signs of 11 rare physical conditions," says Gill, "including cleft lip, spina bifida and serious heart abnormalities." You can see a list of them all in What conditions is the scan looking for? below
"All of these conditions are uncommon," says Gill, "and some of them are very rare. So, for most women, this scan will show that your baby seems to be developing quite normally for your stage of pregnancy."
There is no national data collected on the number of these rare conditions that are spotted at the 20-week scan. But, to help put things in context a bit, in a 2020 study of a group of 15,244 pregnant women in the Oxford area, just over 1% (174) of the group's 20-week scans found a sign of one of them.5
Will I find out the sex of my baby at my 20-week scan?
Yes, it's highly likely sonographer will tell you if you're expecting a boy of a girl – if you'd like to know.
But there are a handful of hospitals that have a policy of not telling you the sex of your baby, even if you ask – in case a mistake is made. That's because spotting whether it's a girl or a boy is not a completely exact science (Gill reckons it's about 95% accurate) and babies sometimes go all shy and cross their legs at the crucial moment).
- Read more about the 3-line method sonographers use to tell if your baby's a boy or a girl
"It should be stressed that telling you the baby's sex is not officially part of the screening programme," says Gill. "Most sonographers are happy to give an opinion, if that is what you would like, but you should check with your hospital or midwife as to the policy of your NHS Trust."
If you don't want to find out the sex, the sonographer won't tell you. But – word to the wise – don't panic if you then see the word 'female' printed out on the top of your scan photos. That's you the word is referring to (because you're the hospital's patient), not your baby. Phew!
How do I prepare for my 20-week scan? What do I need to do beforehand?
Bring along your antenatal notes and wear loose trousers or a skirt and top, rather than a dress – as with the 12-week scan, you'll be asked to lie on your back on a couch and adjust your clothes to expose your belly.
You'll probably also be asked to drink water before your appointment, as having water in your bladder can push your uterus up and help the sonographer get a better scan image.
You don't actually need quite as full a bladder as you did at your 12-week scan6 (because your baby will be so much bigger this time round) but you may find your appointment letter asks you to come with a full bladder anyway. Obviously, it's best to follow any instructions you're given (your sonographer can always ask you to go for a quick wee if needed).
What happens at the 20-week scan?
The procedure will be the same as it was for your 12-week scan: dimly lit room, (cold) gel on your bump, and then a slight pressure as the sonographer passes a handheld transducer over the skin of your belly.
The next thing is the black-and-white image of your baby appearing on the sonographer's screen. Often, you can see all, or part, of the screen too, or it'll be turned towards you after a few moments. Or there may be a separate screen for you to look at.
This is when your sonographer will really have to concentrate hard. "They have to look really carefully at your baby from top to toe," says Jane Fisher, director of the testing-support charity Antenatal Results and Choices (ARC). "There's much more to do than at the 12-week scan."
This means it may be a little while before your sonographer can talk you through what's showing on the screen. So don't panic if there's silence for a bit!
Your sonographer may also spend quite a bit of time looking at one particular thing, like your baby's heart – which at 20 weeks, is about the size of a thumbnail. I understand that this might seem worrying but it's actually normal for sonographers to do this, as they have a lot to look at and they also have to take measurements and look at the blood vessels
This was certainly how it was for Louise, a member of our MadeForMums Top Testers Club, at her 20-week scan. "The sonographer spent at least 10 minutes just looking at the heart," she says, "slowing the machine down, rewinding it, speeding it up and flipping the image over and around. We were starting to panic that she was going to tell us something was wrong but she said she was just counting the blood vessels and stuff."
You may also find your sonographer takes their time over a certain check if they’ve having trouble getting a good picture. "This can happen if your baby's lying in an awkward position," says Gill, "or your body tissue is very dense."
How long does the 20-week scan take?
This scan will probably take longer than your 12-week one, so do expect to be in there for about half an hour.
"This is a very comprehensive scan and there is a lot of work for the sonographer to do," says Gill. "You can expect to be in there for anything up to 30 minutes.
"Also, if the sonographer can't see everything at this scan, they may send you for a walk and then get you back in the room, so you may be there for longer. If that doesn't work, they may suggest that you come back another day to get the rest of the views needed."
What will I be able to see? Will I be able to see my baby's face?
Yes, there's usually a lot more to see this time round. But the amount of detail, says Gill, does vary hugely from pregnant woman to pregnant woman.
"It depends which way your baby is lying, and how much movement they are making at that particular time," she says. "And also if you have a high BMI (body mass index), it can mean that it's harder sometimes is to see because of the way sound interacts with your body tissue."
All things being well, though, you should see much more of your baby than you did at your 12-week scan, including closer-up shots of arms (see picture, above) and the face.
And, if your baby's moving, you may even see some wriggles or kicks, like Danielle, from our MadeForMums Top Testers Club, did:
My 20-week scan went really well today. Everything's looking fine. We saw our baby yawning and it gave us a little wave!
Can I take my partner to the 20 -week scan?
You might want to bring someone with you to share the experience – your partner or another adult family member, maybe. But it's entirely up to you.
Can I take my other children to the 20-week scan?
You'll need to check with your hospital about this one, and you should be prepared for them to say no: quite a few hospitals don't allow small children into the pregnancy ultrasound departments.
"We generally do not recommend bringing your children to the NHS screening scans," says Gill Harrison, "but the policy on this does vary from hospital to hospital. Performing the scan requires intense concentration from the sonographer, so many hospitals take the view that the fewer distractions, the better."
Is the 20-week scan done in 3D?
No. What the sonographer – and you – will see on the screen is a 2D black-and-white image.
It is possible to have a 3D pregnancy scan but not on the NHS; you will need to book and pay for this kind of scan at a private scanning clinic.
Will I get get a photo to keep?
Yes, probably. Most NHS hospitals will let you take away a black-and-white photograph of the scan image once your appointment has ended. It's likely to be a side view of your baby – like the scan pic at the top of this article. Some hospitals will offer you a small set of photos, rather than just the one.
If you're after lots of glossy colour pics, you can consider booking (and paying for) a separate private scan.
Costs for the 20-week scan photo vary, and aren't always flagged up in advance, so do make sure you take some cash with you (some hospitals can't accept card or phone payment).
Can I take my own photo or make a recording?
No. You're usually asked not to take your own video or photos – or record audio of the baby's heartbeat – while you're in the scan room.
Will I find out the results straightaway?
Yes. Most 20-weeks scans show the baby developing as expected for this stage in pregnancy and, if that's the case for your scan, the sonographer will say so.
If, however, the sonographer sees anything of concern, you will be told there and then. At this point, the sonographer may call in a colleague for a second opinion. For more on what might happen next, see What happens if the scan highlights a problem?, below.
Occasionally, the sonographer is unable to get a clear picture of what they need to see. If this happens at your scan, as it did to Melissa, a member of our MadeForMums Top Testers Club, you may be asked to come back for a repeat scan on another day.
"Most of my 20-week scan went well," says Melissa, "but my baby's spine was blocking the sonographer's view of the heart chambers, so I had to book another day to come back."
What conditions are the 20-week scan looking for?
As well as measuring your baby's growth, your sonographer will be looking for signs of 11 rare physical conditions. These are:7
- Open spina bifida
- Cleft lip
- Diaphragmatic hernia
- Serious cardiac abnormalities
- Bilateral renal agenesis
- Severe skeletal dysplasia
- Edwards' syndrome (T18)
- Patau's syndrome (or T13)
Some of these conditions will require treatment or surgery after your baby is born; others may, sadly, be life-limiting or mean your baby will after soon after they're born or may die later in your pregnancy.
You can read more about these conditions in the government information leaflets for parents that we have linked to in each case.
Will the 20-week scan find everything? If the scan result's OK, does it definitely mean there's nothing wrong with my baby?
Very probably. Official figures8 show that 9 out of 10 cases of spina bifida are picked up at a pregnancy ultrasound scan, for example.
But some of the conditions your sonographer is specifically looking for a harder to see: the same figures8 show that the 20-week scan will only detect about 50% of babies with heart defects.
Also, as the scan only looks for certain specific problems and there are other conditions (that might not show up until much later in your pregnancy), it cannot absolutely find everything that might be wrong.
What if I have questions about the comments in my scan report?
After your scan has finished, you may get issued with a scan report (to put with your other antenatal notes). This report will contains lots of measurements and maybe some accompanying comments.
Occasionally, the comments may be worded in a way that might seem worrying or seem to suggest something you weren't made aware of at the scan – you may see, 'head measuring small', for example.
"If you see something like this," says Midwife Pip, a practising NHS midwife and expert antenatal and postnatal educator, "please know that there is a wide range of 'normal' and if there were any concerns, it would almost certainly have been mentioned to you at the time of your scan.
"But if there's a comment you don't understand or that you would like explained to you, please do speak to your midwife or obstetrician and ask."
What happens if there are signs of a problem? What then?
If your 20-week scan picks up anything of concern, it's usually for one of the two main reasons:
- Your baby seems to be measuring 'small for dates'. This could be an indication of problems with your baby or with your placenta. Or it could just be that your baby is perfectly healthy but currently a little smaller than expected.
What happens next: You may be offered further tests or further scans. You'll be given plenty of information about any follow-up tests and scans that are suggested, and you'll be able to discuss the best next steps with your midwife or consultant.
- Your sonographer has seen one of the specific physical conditions the scan is screening for. "This could be an untreatable condition that may, unfortunately, mean your baby can't survive," says ARC's Jane Fisher. "Or it could be a treatable condition – which means your baby will need surgery or treatment when they are born, or maybe even in the womb. (You can see more on these conditions in What conditions is the 20-week scan looking for?, above).
What happens next: You'll be given plenty of information and support and the opportunity to discuss the best next steps with your midwife or consultant. You may also want to call the trained staff at the ARC helpline on 0207 713 7486 or send them a text on 07908 683004 (Monday to Friday, 10am to 5.30pm).
Will I be offered any more pregnancy scans after 20 weeks?
There are are no further routine NHS pregnancy scans. You may be offered further scans later in your pregnancy, depending on your health or if your antenatal team feel they need to check your baby's growth.
About our ultrasound expert Gill Harrison
Gill Harrison is a highly experienced sonographer and radiographer, currently working as the Professional Officer (Ultrasound) at the Society and College of Radiographers. She was previously an Associate Professor at City, University of London and responsible for leading the medical ultrasound programme. She is a lead accreditor and external examiner, assessing the competency of ultrasound students and qualified sonographers in UK universities and hospitals. She is Chair of the Health Education England's Sonographer Training Group and was previously Chair of the European Federation of Radiographer Societies' Working Group for Ultrasound Surveys (2019 to 2022) and Chair of the Society and College of Radiographers' Ultrasound Advisory Group.
About our antenatal screening expert Jane Fisher
Jane Fisher has been Chief Executive of the national charity Antenatal Results and Choices (ARC) since 2004. ARC provides impartial information to those going though antenatal screening and offers support to anyone faced with decisions about next steps as a consequence of screening. ARC also offers training to healthcare professionals in the field, and Jane has published many academic papers on antenatal screening, prenatal diagnosis and fetal development.
About our expert midwife Midwife Pip
Pip runs online antenatal and postnatal courses and believes passionately that, with the right support and with honest and evidence-based information, all births should be positive. You can find her on Instagram @midwife_pip.
1. Safety of ultrasonography in pregnancy: WHO systematic review of the literature and meta-analysis. Torloni et al. Ultrasound in Obstetrics and Gynaecology. First published 17 March 2009; doi.org/10.1002/uog.6328.
2. Warning sounded over commercial ultrasound in pregnancy. The Lancet. 3 January 2015
3. Ultrasound exams: frequently asked questions. The American College of Obstetricians and Gynaecology. Last reviewed October 2021.
4. Ultrasound scans in pregnancy. NHS online
5. How often do we incidentally find a fetal abnormality at the routine third-trimester growth scan? A population-based study. Drukker et al. Am J Obstet Gynecol. 2020 Dec;223(6):919.e1-919.e13. doi: 10.1016/j.ajog.2020.05.052.
6. Ultrasound scans during pregnancy. NHS Inform
7. 20-week screening scan. NHS online
8. 11 physical conditions: 20 week scan. NHS England. August 2022
Pics: Getty Images
Helen is author of the classic advice book Parenting for Dummies and a mum of 3. Before joining MadeForMums, she was Head of Community at Mumsnet and also the Consumer Editor of Mother & Baby.
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