The Nuchal Scan, Step by Step

A nuchal scan is the first trimester ultrasound appointment where your baby is measured and, if you choose, screened for certain chromosomal conditions. For many parents it is also the first proper look at their baby moving on screen. This guide walks through the appointment itself, step by step, from booking to results, so you know exactly what to expect on the day. It is general information, so always follow the guidance of your own midwife or doctor.

What a nuchal scan is and why it is offered

A nuchal scan is an ultrasound performed in the first trimester. Its everyday jobs are to confirm how many weeks pregnant you are, check how many babies you are carrying and confirm the heartbeat. If you have chosen screening, the sonographer also measures the nuchal translucency, the small fluid space at the back of the baby's neck, which feeds into a wider screening test. If you want the background on that measurement itself, see our guide to what nuchal means.

Because it lines up with the dating scan, many clinics roll the two into one appointment. Some services call the same imaging a nuchal ultrasound, and it also overlaps with what many people simply call the 12 week scan. They all describe the same gentle scan around the same stage.

When the scan happens, week by week

Timing matters for a nuchal scan because the neck measurement is only reliable in a specific window.

• 11 weeks to 13 weeks plus 6 days: the standard window, matching a crown to rump length of roughly 45 to 84 millimetres.
• Before 11 weeks: the baby is usually too small for a reliable neck measurement, so the scan is booked a little later.
• After 14 weeks: the nuchal window has passed, and a different screening test using a blood sample is offered instead.

If you booked late or the baby is measuring smaller than expected, the clinic may simply rearrange for a few days later. That is common and is about getting an accurate measurement, not a sign of a problem. Our overview of scans during pregnancy shows how this fits the wider schedule.

Booking and preparing for the day

Once your pregnancy is confirmed, your midwife or clinic usually arranges the scan for you, or you may book a private appointment. When you book, ask whether they want you to arrive with a full bladder, since a comfortably full bladder lifts the uterus into a better viewing position for an abdominal scan. Instructions vary, so it is worth checking rather than guessing.

• Wear a two piece outfit so your abdomen is easy to reach.
• Bring your maternity notes and any earlier scan or booking paperwork.
• Allow time to drink water beforehand if a full bladder is requested.
• Decide in advance whether you want screening, so you can discuss it calmly on the day.

What happens during the appointment

When you are called in, you lie back on a couch and the sonographer tucks tissue around your clothing to protect it from the gel. They squeeze a little warm gel onto your abdomen and glide a handheld probe across it, watching the screen as they work. The scan is completely painless, though a full bladder can feel a bit uncomfortable and you can usually empty it partway through if needed.

The sonographer measures the baby from crown to rump to confirm your dates, checks the heartbeat, counts how many babies are present, and looks at the early structures that are visible at this stage. If you are having screening, they take the nuchal measurement when the baby is in a good side on position. They may ask you to cough gently, wiggle or come back shortly if the baby is not cooperating, which is completely normal.

Getting your results

Some results are shared with you straight away. The sonographer can usually confirm your dates, the heartbeat and the number of babies before you leave. Screening results are different, because the nuchal measurement is combined with your age and a blood test to produce a single chance figure. The NHS describes this combined test as the standard first trimester screen, and the final result often follows by phone or letter within a couple of weeks.

A result is given as a chance, such as one in a certain number, for conditions including Down's syndrome. A higher chance result means further options may be offered, not that a diagnosis has been made. A lower chance result is reassuring but does not rule everything out. Our guide on the nuchal measurement explains how to read these numbers.

If more information is needed

If your combined test suggests a higher chance, your team will talk you through the next steps without pressure. These may include a non invasive prenatal blood test, or a diagnostic test such as chorionic villus sampling or amniocentesis, which can give a definite answer. A midwife or genetic counsellor can explain what each option involves so you can decide what is right for you.

It is worth remembering that screening is a choice at every stage. You can accept a first trimester scan for dating and reassurance while declining the chromosomal screening, or take the screening and then decide separately about any further tests. None of these steps is automatic, and you set the pace.

Choosing where to have your scan

Most people have their nuchal scan through their standard maternity service, but some choose a private appointment for convenience or timing. If you go private, look for a clinic with qualified sonographers, clear information about what is included, and a sensible plan for what happens if screening suggests a higher chance. Our guide to a private ultrasound explains what to check before you book.

Wherever you go, a good clinic will be happy to answer questions, explain the limits of screening honestly, and make sure any result is followed up with your maternity team. If a service promises certainty from a scan, treat that as a warning sign, because screening deals in probabilities rather than guarantees.

Frequently asked questions

When is a nuchal scan done?

A nuchal scan is usually done between about 11 weeks and 13 weeks plus 6 days, when the baby measures roughly 45 to 84 millimetres from crown to rump. This window gives a reliable nuchal translucency measurement. Before 11 weeks the baby is often too small, and after 14 weeks a different screening test is used.

How long does a nuchal scan take?

The appointment usually lasts around 20 to 30 minutes, though it can be longer if the baby is not in a good position and the sonographer needs to wait for it to move. The scan itself is painless. You may be asked to arrive with a comfortably full bladder for a clearer view.

Do I have to have the screening part?

No. You can choose to have the scan for dating and reassurance while declining the chromosomal screening, or you can accept both. Screening is always optional, and it helps to decide in advance so you can discuss it calmly with the sonographer. Your midwife can talk through what each choice means.

When will I get my results?

Your dates, the heartbeat and the number of babies are usually confirmed on the day. The combined screening result, which mixes the nuchal measurement with your age and a blood test, often follows by phone or letter within a couple of weeks. Your clinic will tell you how and when to expect it.

Is a nuchal scan safe?

Yes. It is a standard ultrasound that uses sound waves rather than radiation, and it is painless with no known risk to you or your baby. Any decision about further, more invasive tests after screening is separate and would be discussed with you in detail before you agree to anything.