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What happens at your 20 week scan?

Your 20 week scan is an exciting opportunity to see how your baby is growing. We look at what a sonographer will check for at 20 weeks

The process of your 20-week scan will be much the same as the scan you had at 12 weeks. It can be amazing to see how your baby is growing and developing, and many parents eagerly look forward to this scan. Not least because they might be able to find out their baby’s sex (as long it is your hospital’s policy to let you know if you wish) (NHS, 2017).

When does my second scan take place?

The second scan many pregnant women have is between 18 and 21 weeks.

This can be called an anomaly scan or mid-pregnancy scan. This scan is routinely offered at this stage to check for abnormalities or anomalies in the baby (NICE, 2008; NHS, 2018c).

For more on why you’ll have a scan and what they’re used for, see our article on What happens at your 12-week scan.

What does the anomaly (20 week) scan check for?

The sonographer will use this scan to examine the baby's size and position. They’ll also check if their brain, heart, lungs and other internal organs are developing as they would expect.

They are also looking for signs of 11 specific conditions, some of which are more obvious than others, such as spina bifida. About nine out of 10 of the babies diagnosed with a particular condition have spina bifida.

Other conditions will be more difficult to diagnose, like heart defects. In this case, you might have a foetal echocardiogram (sometimes called a cardiac echo). This test creates a four-chamber view of your baby’s heart (NICE, 2008; NHS, 2018c).

Some conditions are harder to pick up at the dating scan but might be more apparent at the anomaly scan. For example, Edward’s syndrome is usually detected during first trimester antenatal screening but is often more obvious at the 18 to 20 week scan (Healthtalk, 2017).

What can make the scanning process more complicated?

As with the dating scan, it might be that the sonographer cannot get a clear picture of your baby. This would be for the same reasons as with your dating scan, see here for more details on why (NHS, 2017).

If this happens, the sonographer might ask you to come back after a short break. Otherwise, they might book a repeat scan if they're not able to gather enough detail from the pictures (NICE, 2008; NHS, 2017).

Do I have to have the scan? What might I need to consider?

Like with the dating scan, you don’t have to have an anomaly scan.

A healthcare professional should provide information to pregnant women about the purpose and implications of the anomaly scan. This will enable them to make an informed choice about whether or not to have the scan to identify foetal anomalies. Depending on results, you might be offered further tests such as amniocentesis (RCOG, 2010; NHS, 2018b).

Of the 800,000 women in the UK who become pregnant each year, around 40,000 will be told there is a chance that their baby has a serious foetal anomaly (ARC, 2019). This may result in or lead to further decisions that could be difficult and emotional.

Some parents appreciate being forewarned but you might also consider that this knowledge could impact your experience of pregnancy.

When will I find out the results?

If there are no abnormalities or concerns, the sonographer can let you know the results straight after the scan (NHS, 2018b).

What happens after the scan?

Where the sonographer suspects problems, they may ask a second opinion from a colleague and another test might be offered (NHS, 2017). It is likely you will be invited to discuss your options with your midwife and/or a consultant (NHS, 2017).

What support is offered in case of problems?

All sonographers are trained to discuss any abnormalities or concerns resulting from the scans. Despite this, where abnormalities are found, it might be difficult to say why this has happened and make a firm diagnosis as a result.

If the news is potentially destressing and parents wish to discuss it further, a medical professional should be available. An appointment would be booked within a few days (Healthtalk, 2017; ARC, 2019).

Try to remember that there is support out there including:

What about scans in late pregnancy (after 24 weeks)?

Although not usually offered on the NHS if your pregnancy is without complications, you might decide to have or be offered a scan in late pregnancy.

Here are a few things to consider when deciding whether to have a scan later on in pregnancy (after 24 weeks):

  • Scans in late pregnancy can help assess the condition of babies with known complications, or identify problems that are otherwise not apparent.
  • If changes are identified, then this might lead to improved care and better outcomes for babies.

(Bricker et al, 2015)

On the other hand:

  • Carrying out late pregnancy scans for all women is controversial, as this might mean increased interventions for women and their babies without benefit for them.
  • Evidence shows that a routine ultrasound after 24 weeks' gestation in low-risk women does not provide any benefit for mum or baby. So late pregnancy scans are not offered as a matter of course.

(Bricker et al, 2015)

This page was last reviewed in May 2019

Further information

Our support line offers practical and emotional support with feeding your baby and general enquiries for parents, members and volunteers: 0300 330 0700.

We also offer antenatal courses which are a great way to find out more about birth, labour and life with a new baby.

Make friends with other parents-to-be and new parents in your local area for support and friendship by seeing what NCT activities are happening nearby.

ARC. (2019) Tests explained. Available at: [Accessed 20th May 2019]

Bricker L, Medley N, Pratt JJ. (2015) Routine ultrasound in late pregnancy (after 24 weeks’ gestation) to assess the effects on the infant and maternal outcomes. Available at:… [Accessed 17th May 2019]

Buckley S. (2016) Ultrasound scans in pregnancy – your questions answered! Available at:… [Accessed 15th May 2019]

Department of Health and Social Care. (2016) Safer screening for women Available at:… [Accessed 28th May 2019]

Healthtalk. (2017) Ending a pregnancy for fetal abnormality. Available at:… [Accessed 17th May 2019]

Payne J. (2016) Amniocentesis. Available at: [Accessed 26th May 2019]

NICE. (2008). Antenatal care for uncomplicated pregnancies, Clinical guideline [CG62]. Available at: [Accessed 25th May 19]

NHS. (2017) Ultrasound scans in pregnancy. Available at:… [Accessed 15th May 2019]

NHS. (2018a) Screening for Down’s Edwards and Pataus’ syndrome Avaliable at:… [Accessed 26th May 2019]

NHS. (2018b) Ultrasound Scan Available at: [Accessed 20th May 2019]

NHS. (2018c) Your pregnancy and baby guide. Available at: [Accessed 20th May 2019]

NHS; Public Health England. (2019) Screening tests for you and your baby. Available at: [Accessed 20th May 2019]

RCOG. (2010) Amniocentesis and chronic villus sampling. Available: [Accessed 27th May 2019]

RCOG. (2015) RCOG release: The use of ultrasound before 10 weeks gestation is examined in a new scientific opinion paper. Available at:… [Accessed 17th May 2019]

Salvesen K, Lees C. (2009) Ultrasound is not unsound, but safety is an issue. Available at: [Accessed 17th May 2019]

Whitworth M, Bircher L, Mullan C. (2015) Routine compared with elective ultrasound in early pregnancy: pregnancy and childbirth. Available at:… [Accessed 17th May 2019]


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