What happens at the 20-week ‘anomaly scan’?

The 20-week scan is also known as the ‘anomaly scan’. Here’s what to expect from the 20-week scan and what it can tell you about your baby.

5 min read

What happens at the 20-week ‘anomaly scan’?

The 20-week scan is also known as the ‘anomaly scan’. Here’s what to expect from the 20-week scan and what it can tell you about your baby.

5 min read

What is the 20-week scan?

This is a detailed ultrasound scan that looks at your baby’s development. It will also check your uterus (womb) and placenta to rule out problems. It is sometimes also called the mid-pregnancy scan.

When will I have my 20-week scan?

This diagnostic scan can be carried out from 18 to 21 weeks, so don’t worry if yours isn’t at exactly the 20-week point.

Do I have to have an anomaly scan?

No, all scans and tests in pregnancy are completely voluntary. However, the 20-week scan is very useful for identifying the chances of abnormalities and the general health of both you and your baby. You will be asked to give your consent for this, as it is a medical examination.

What happens at the 20-week anomaly scan?

You will visit your local hospital for this check and be asked to lie on a couch with your belly exposed – it’s best to wear a top you can pull up and trousers or skirt you can pull down. A specially trained medic called a sonographer will carry out the examination. They will tuck some tissue into your clothes to protect them from the gel that they smear on your tummy. They then hold a probe to your skin – the gel ensures a good image is captured.

It won’t hurt, though you may feel some pressure as the sonographer moves the probe around to get the best image. You may be asked to have this test with a full bladder, so make sure you know before you visit and have plenty of water with you!

What to expect from your 20-week scan

Your 20-week scan checks several things:

  • all parts of your baby’s developing body

  • the position of your placenta

  • the sex of your baby

In most cases, the ultrasound scan will show that your baby is developing completely normally. It can also offer a better guess at your due date, as the sonographer can measure your baby to see how far along you are in pregnancy.

What does the anomaly scan look for?

The scan is useful to diagnose the following conditions:

  • Cleft lip and palate

  • Neural tube defects including spina bifida and anencephaly

  • Cardiac problems

  • Abdomen problems such as hernias of the diaphragm, exomphalos and gastroschisis

  • Edwards’ and Patau’s syndrome

  • Kidney problems

  • Skeletal dysplasias

Can the anomaly scan pick up all birth defects?

Most women only need two scans in each pregnancy, but if your medical team are even the slightest bit concerned, you’ll be given further scans and tests along the way. This is because not all conditions can be pinpointed at the 20-week scan, especially if they do not have a physical appearance. Some such as spina bifida, a defect of the spinal cord, can be clearly seen, though heart conditions may be more difficult to see for example. For some conditions, such as cleft lip or club feet, parents can plan for their baby having corrective surgery soon after birth.

Can the scan tell me the sex of my baby?

If you want to know whether you’re having a girl or a boy, you may be able to find out at the 20-week scan, though occasionally the baby is in too difficult a position for the sonographer to be sure. If you don’t want to know your baby’s sex, make sure you tell the sonographer as soon as you come into the room!

What if the sonographer can’t see the baby properly?

Sometimes your baby’s position, excess body fat or scar tissue may make it hard to see the baby, so the sonographer may suggest a trans-vaginal scan instead, where a small probe is inserted into your vagina so the baby can be seen more easily.

What to bring to the 20-week scan

Depending on the scan you are going for you may be asked to your hospital and pregnancy notes. Sometimes it can take a while, so a drink of water is recommended. You can also bring some healthy snacks for once it's over.

Who can I bring to the 20-week scan?

Usually, you can bring your partner, or another friend or relative with you (the rooms tend to be small, so just one person). It’s not advisable to bring other children you have, so arrange for them to be cared for while you’re at the scan.

With some hospitals still having Covid restrictions, sadly it may mean that you attend the scan alone.

What questions should I ask at the 20-week scan?

Usually, your sonographer will answer all your questions, telling you the results of the test. It pays to be well-informed so that you do not leave with unanswered questions, so you might like to ask:

  • Am I measuring correctly for my dates?

  • Is the umbilical cord, the placenta and its position in the uterus OK?

  • Does my baby have any abnormalities?

  • Is my baby growing at the correct rate?

  • What sex is my baby?

When will I get the results of the anomaly scan?

Your sonographer will give you the results at the end of the scan. If everything is clear, fantastic! Don’t forget to ask for a printed image of your scan to take home to show friends and family. If there is any kind of issue that needs addressing, they will refer you back to your medical team for more tests or counselling. Never be afraid to ask questions or air your worries – the experts are there to support you on your pregnancy journey.

This content should not substitute medical advice from your personal healthcare provider. Please consult your healthcare provider for recommendations/diagnosis or treatment.
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