Pregnancy and obstetric ultrasound (Obstetric ultrasonography (pregnancy ultrasound scan))
A scan that uses sound waves (no radiation) during pregnancy to check the baby's development, dates and wellbeing — but it cannot find everything or guarantee a healthy baby.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- Pregnancy ultrasound uses sound waves, not radiation, and is a routine, important part of NHS antenatal care.
- A normal scan is reassuring but does NOT guarantee a healthy baby, and it cannot find every condition.
- Routine NHS scans usually include a dating scan (about 11–14 weeks) and an anomaly scan (about 18–21 weeks); extra scans need a reason.
- It is your choice whether to have each scan — ask what it is looking for and what happens if something is found.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your radiologist will give you advice for your situation.
Confirms how many weeks pregnant you are and your due date.
Ultrasound is not a diagnostic test for chromosomal conditions on its own — that needs screening blood tests or a diagnostic test such as amniocentesis or...
The sonographer often talks through the main findings as they go, though they may be quiet at times while concentrating on measurements.
Clear, kind explanation of what the scan did and did not show.
The sonographer often talks through the main findings as they go, though they may be quiet at times while...
You can wipe off the gel, dress and go home or back to work. There are no restrictions afterwards.
You may be offered a repeat scan or referral to a fetal medicine specialist, often within a short time, to look...
If the scan was part of combined screening (for example for Down's syndrome), the result is usually given...
What is a pregnancy (obstetric) ultrasound?
A pregnancy ultrasound uses high-frequency sound waves, not X-rays or radiation, to create a moving picture of the baby, the placenta and the womb. A specially trained sonographer (often a radiographer or midwife sonographer) moves a probe over your tummy, or sometimes uses a gentle internal probe early in pregnancy, while watching the images on a screen.
On the NHS in England you are usually offered at least two routine scans: a dating scan at around 11 to 14 weeks, which confirms your due date and checks for more than one baby, and a mid-pregnancy or 'anomaly' scan at around 18 to 21 weeks, which looks in detail at how the baby is growing and developing. Extra scans may be arranged if there is a specific reason.
Scans can be reassuring and are an important part of antenatal care, but they have real limits. A normal scan does not guarantee a healthy baby, and not all conditions can be seen — some are easier to detect than others, and some only show up later or not at all. The scan is a screening tool, not a promise.
It is your choice whether to have each scan. You can ask what a particular scan is looking for, what it cannot tell you, and what would happen if something is found, before you decide.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Screening scan vs diagnostic test
| Point | Screening scan | Diagnostic test |
|---|---|---|
| What it does | Looks for signs that need a closer look | Aims to give a definite answer |
| Example | Anomaly scan, combined screening | Amniocentesis, CVS |
| Certainty | Cannot find everything | More definite, but carries its own risks |
| Your choice? | Yes | Yes |
A scan is a screening tool. If it raises a concern, you may be offered a diagnostic test, which has its own benefits and risks to discuss.
Preparing for your scan
- Check the appointment letter — some scans ask you to arrive with a comfortably full bladder, which can improve the early view.
- Wear a two-piece outfit so your tummy can be reached easily.
- Think in advance about whether you want to know the baby's sex, where this is offered, and whether you want to be told everything seen.
- Bring your maternity notes and details of any previous pregnancies or scans.
- You can usually eat and drink normally; there is no fasting.
- Decide who, if anyone, you want with you, and check the unit's policy on visitors and photos.
- Ask beforehand what this particular scan is looking for and what it cannot tell you.
What happens
For most scans you lie on a couch and the sonographer puts warm gel on your tummy, then moves a probe over the skin to see the baby on a screen. Early in pregnancy a clearer view sometimes needs a gentle internal (transvaginal) probe, which you can decline.
The sonographer takes measurements and looks carefully at different parts of the baby, the placenta and the fluid around the baby. They concentrate hard during this, so there may be quiet periods. The scan can take longer if the baby is lying in an awkward position, and you may be asked to move, walk around or come back later.
The sonographer can usually talk through the main findings as they go. If they see something that needs a closer look, they will explain this and arrange a further scan or a referral to a fetal medicine specialist. Some results, and any screening calculations, are reviewed and reported afterwards rather than given fully on the day.
Is this scan right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- Ultrasound is not a diagnostic test for chromosomal conditions on its own — that needs screening blood tests or a diagnostic test such as amniocentesis or CVS.
- A non-medical 'keepsake' scan is not a substitute for NHS antenatal scans and should not be used for reassurance.
- A scan cannot reliably exclude every fetal condition, so it is the wrong tool to seek a guarantee of a healthy baby.
- Urgent symptoms such as heavy bleeding, severe pain or reduced movements need direct contact with the maternity unit, not a routine booked scan.
Delay or rearrange if…
- There is a more urgent obstetric concern that needs assessment first, such as bleeding or severe pain.
- Key information, such as your dates or previous notes, is missing and would change what is done.
- You feel unsure and want more time to decide whether to have a particular scan or screening.
- The baby's position prevents a full view, in which case the scan may be repeated rather than rushed.
Alternatives to discuss
- Declining a particular scan or screening after understanding what it offers.
- Midwife-led monitoring with attention to symptoms and baby movements between scans.
- Combined or quadruple screening blood tests, and NIPT where appropriate, for chromosomal conditions.
- Diagnostic tests (amniocentesis or CVS) if a more definite answer is needed, with their own risks discussed.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- Confirms how many weeks pregnant you are and your due date.
- Checks whether you are expecting more than one baby.
- Looks at the baby's development and can detect a number of physical conditions before birth.
- Checks the position of the placenta and the baby's growth and wellbeing later in pregnancy.
- Can find problems early enough to plan care, treatment or extra support.
- Uses no radiation and is considered safe for mother and baby when done for a medical reason.
Risks & complications
- Being asked to return or rescan because the baby is in an awkward position
- Finding something uncertain that needs another scan or a specialist opinion
- Anxiety while waiting for further checks or results
- A condition not being seen on the scan even though it is present (a 'false negative'), because not everything can be detected
- A finding that looks abnormal but turns out to be normal (a 'false positive'), causing worry and further tests
- An unexpected or 'incidental' finding that is difficult to interpret
- Being told difficult or unexpected news that the baby has a serious problem
- A serious condition that develops or only becomes visible after the scan
The biggest thing to understand is what a scan cannot do. It cannot find every condition, some problems are easier to see than others, and a normal scan does not guarantee a healthy baby. Non-medical 'keepsake' or commercial scans are not a substitute for NHS antenatal scans and should not be relied on for reassurance. If you are worried that something is not right at any point in pregnancy, contact your midwife or maternity unit rather than waiting for the next scan.
Published figures to discuss
Detection rates vary a great deal between conditions, how clearly the baby can be seen, the stage of pregnancy and the skill of the sonographer. Some structural conditions are seen in most cases, while others are detected far less often, and some are not visible at all. False reassurance and anxiety from uncertain findings are both real. The figures below come from the NHS and reflect why a normal scan cannot guarantee a healthy baby.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Detection of open spina bifida at the 20-week scan | About 9 in 10 cases (around 90%) noted | This is one of the more clearly seen conditions; detection is still not 100%. | NHS — Ultrasound scans in pregnancynhs.ukPublished figure |
| Detection of serious heart (cardiac) conditions at the 20-week scan | About 1 in 2 cases (around 50%) | Heart conditions are harder to see, so many are not detected before birth. | NHS — Ultrasound scans in pregnancynhs.ukPublished figure |
| Detection of all congenital conditions at the anomaly scan | Incomplete; some conditions develop later or are not visible on ultrasound | A normal scan is reassuring but not a guarantee of a baby without health problems. | NHS — Ultrasound scans in pregnancynhs.ukSource-linked context |
| Need for repeat scan because views are limited | Common enough in routine practice | Baby position, gestation, maternal body habitus and scar tissue can limit views. | Guide sourcesClinical context |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is no physical recovery from the scan itself — you can carry on as normal straight away. 'Afterwards' is mainly about understanding what the scan did and did not show, and what happens next if anything needs following up.
- No physical after-effects at all
- Being asked to return because of the baby's position
- Some natural worry while waiting for a further scan or screening result
- Continuing all your usual pregnancy care and appointments
Aftercare
- Carry on as normal — there are no physical restrictions after a scan.
- Make sure you understand what this scan looked at and what it could not tell you.
- Keep all your routine antenatal appointments, whatever the scan showed.
- If you were offered a further scan, screening test or referral, make sure you know when and where.
- Know how to contact your midwife or maternity unit between appointments.
- Report reduced baby movements, bleeding, severe pain or feeling unwell straight away — do not wait for the next scan.
- Be cautious about private 'keepsake' scans as a source of reassurance; they do not replace NHS scans.
- Appointment letter checked for bladder and timing instructions
- Maternity notes to bring
- Decision made about knowing the baby's sex, if offered
- Decision about who comes with you
- Questions written down about what the scan can and cannot show
- Maternity unit contact number saved
⚠ Get urgent help if…
- Reduced or changed baby movements — contact your maternity unit straight away, day or night
- Vaginal bleeding or fluid leaking from the vagina
- Severe or persistent tummy pain
- A severe headache, vision changes, or sudden swelling of the face, hands or feet
- A high temperature or feeling generally unwell
- Any strong feeling that something is not right with you or the baby
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your radiologist gives you.
Results & realistic expectations
A reassuring scan means that, at that point, the things the sonographer looked at appeared to be developing as expected for the stage of pregnancy. For the mid-pregnancy scan this includes a detailed look at the baby and a check for 11 specific physical conditions, but some conditions are seen far more clearly than others.
It is essential to understand the limits. The scan is a screening tool, not a guarantee: it cannot find every condition, it cannot promise a healthy baby, and some problems only appear later or cannot be seen at all. If a concern is found, it usually means a closer look or a diagnostic test is needed — not a definite diagnosis on its own. Your midwife or a fetal medicine specialist will explain what any finding means and what your options are.
Each scan reflects the pregnancy at that moment, so reassurance from one scan does not cover the whole pregnancy. That is why antenatal care continues with checks of your wellbeing and the baby's growth, and why new symptoms should always be reported. As pregnancy progresses, further scans may be arranged if there is a medical reason.
Related tests, treatments or support
Pregnancy scans are part of a wider antenatal care package that includes midwife checks, blood tests and screening. The dating scan may be combined with blood tests as part of combined screening for Down's, Edwards' and Patau's syndromes. If a scan raises a concern, it may be followed by a specialist scan or a diagnostic test such as amniocentesis or chorionic villus sampling (CVS), which carry their own small risks to discuss.
Follow-up & long-term care
How results are handled depends on the scan. The sonographer usually shares the main findings of a dating or anomaly scan during the appointment. Screening calculations and some detailed findings are reviewed afterwards and given to you in the way your unit explains. If anything needs following up, you should be told clearly when and where your next scan, test or appointment will be, and who to contact in the meantime.
Repeat, follow-on and what comes next
- Being asked back for a repeat scan because of the baby's position is common and usually not a worry.
- An uncertain finding often needs a more detailed specialist scan rather than a single answer.
- Some conditions only become visible later in pregnancy or after birth.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- Clear, kind explanation of what the scan did and did not show.
- A defined plan and timing for any further scan, screening result or specialist referral.
- A named maternity contact for worries between appointments.
- Sensitive, well-supported communication if difficult news needs to be given, with time to ask questions.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- The type of scan (early, dating, detailed anomaly, growth or specialist fetal medicine scan)
- Whether a fetal medicine specialist or consultant performs or reviews it
- Whether screening blood tests or calculations are included
- Whether images, prints or recordings are part of the package
- The length and detail of the scan and any report
- Any follow-up scan or specialist consultation needed
- Which scan is included and exactly what it checks
- Who performs and reports the scan and their qualifications
- Whether a written report goes to your midwife or maternity team
- What happens, and what it costs, if a further scan or referral is needed
- Whether the scan counts towards your NHS antenatal care or is separate
- How and when you receive any results
On the NHS? NHS and HSC maternity care, including routine pregnancy scans, is provided according to clinical need, and care that is urgent or immediately necessary must never be delayed or withheld because of charging. For most people who normally live in the UK this care is free, but whether it is free depends on where you normally live, your immigration status, and the rules in the UK nation where you are treated — some overseas visitors can be charged. If you are unsure, ask the maternity unit's overseas-visitor or charging team, and never delay seeking maternity care. Extra growth or 'reassurance' scans without a medical reason, and keepsake scans, are usually private.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Believing a normal scan guarantees a healthy baby.
- Not being told that a scan is screening, not diagnosis, and that a finding may lead to further tests.
- Not understanding the difference between a screening scan and a diagnostic test before agreeing.
- Relying on a private keepsake scan instead of NHS antenatal scans.
- Not knowing in advance how and when difficult findings would be discussed.
Marketing red flags
- Private scans advertised as proving your baby is healthy.
- 'Reassurance' or '4D' packages promoted as medical screening.
- Selling extra scans with no medical reason as routine.
- Guaranteeing the baby's sex with certainty.
- Discouraging or replacing your NHS antenatal scans.
Choosing a specialist safely
- Check the radiologist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the radiologist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good radiologist will welcome every one of these.
- What exactly is this scan looking for, and what can it not tell me?
- If something is found, what would happen next and what are my choices?
- Will this scan be part of screening, and when and how will I get those results?
- Can you explain what a 'screening' result means compared with a diagnostic test?
- Who do I contact if I am worried about the baby between scans?
- Do I have to decide about knowing the baby's sex, and can I change my mind?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the radiologist who carries out my scan, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this scan not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
Is ultrasound safe for my baby?
Does a normal scan mean my baby is definitely healthy?
Do I have to have the scans?
Are NHS pregnancy scans free?
Can the scan tell me the sex of my baby?
What is the difference between a screening scan and a diagnostic test?
Are private 'reassurance' or keepsake scans worth it?
What should I do if I am worried between scans?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: NHS — Ultrasound scans in pregnancy NHS — 20-week screening scan GOV.UK — Fetal anomaly screening programme handbook RCOG — Information for pregnant women Tommy's — Ultrasound scans in pregnancy GOV.UK — Overseas-visitor NHS charging (England) nidirect — Health services for visitors (Northern Ireland)
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
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