Articles

Key takeaways

• The 20-week scan checks your baby's development and health.
• It screens for signs of 11 specific physical conditions.
• Most scan results show that babies are developing normally.
• You can often find out your baby's sex, but it's not guaranteed.

What is the 20-week anatomy scan?

The 20-week scan is also known as the mid-pregnancy, anatomy, or anomaly scan. It usually takes place between 18 and 21 weeks of pregnancy. This scan checks if your baby could have a condition affecting their health and development.

The sonographer will take measurements and check your baby's growth. They will also look at the health and position of your placenta. The scan checks for signs of 11 different conditions.

Some conditions are seen more clearly than others. The scan may not find everything, but it is the best way to find any conditions. This information helps you and your care team to plan for your baby's arrival and any care they might need.

What the sonographer looks for

The sonographer will carefully check your baby from head to toe. This includes looking for signs of 11 rare conditions. They will examine:

• Brain – To check for normal development and structure.
• Heart – To ensure the four chambers and major blood vessels are forming correctly.
• Spine – To look for conditions like spina bifida. This is where the spinal cord does not close properly.
• Limbs – To check the development of arms, legs, hands, and feet.
• Face – To look for conditions such as a cleft lip.
• Internal organs – Including the kidneys, stomach, and bowel, to ensure they are developing as expected.
• Placenta position – To check where the placenta is located in the womb.
• Amniotic fluid – To assess the amount of fluid surrounding the baby.
• Umbilical cord – To ensure it has the correct number of blood vessels.

Understanding your results and the scan's limitations

You will be told the results of your 20-week scan after all checks are complete. Most people are told their baby does not have any signs of a condition. Most scans show that the baby is developing normally.

If signs of a condition are found

Sometimes, the scan may show signs that your baby could have a health condition. The sonographer might ask for a second opinion from another staff member. You may be offered further tests to get more information.

You may be offered tests that can give a more definite answer (known as diagnostic tests). These could include amniocentesis, a test using a fine needle to take a small sample of the fluid around your baby. Another option is chorionic villus sampling, which involves taking a tiny sample of the placenta.

These diagnostic tests can confirm if a genetic condition is present. It is important to know that these tests carry a small risk of miscarriage.

What happens next

Your specialist will talk you through this in detail. They will give you all the information and support you need to decide what is right for you.

You will be referred to a specialist to discuss the findings. They will give you more information to help you decide about further tests.

Understanding variants

Occasionally, the sonographer might notice a 'variant'. This is something that looks a little different from the usual. Most of these are completely harmless and just part of your baby's unique development. In rare cases, a variant can be a sign of another condition. Your care team might suggest more tests or follow-up scans to be sure.

Scan limitations

The 20-week scan cannot find all conditions. Some conditions can be seen more clearly than others. Tell your midwife if you have any symptoms you are worried about. You should also tell them if something does not feel right.

Preparing for your scan and finding out the sex

There are a few things you can do to prepare for your 20-week scan.

1. Arrive for your appointment early.
2. Wear loose, comfortable clothing, as you'll need to uncover your tummy for the scan.
3. Take out any belly piercings you have.
4. Bring your maternity notes with you if you have paper notes.
5. Check with the hospital or clinic if you need a full bladder before the scan.
6. Ask if you will need to pay for pictures of your baby.

You can bring someone to the scan with you. Most hospitals do not allow children, so check with the clinic beforehand.

Finding out the sex

Finding out your baby's sex is not part of the NHS screening programme. However, you may be able to find out during the 20-week screening scan. This depends on your hospital's policy.

Tell the sonographer at the start of the scan if you would like to know. It is not always possible for the sonographer to be 100% certain about your baby's sex. Your baby might be lying in a position that makes it difficult to tell.

Some hospitals also have a policy of not telling parents the baby's sex.

The main reason for the scan is to check your baby's health and growth. Occasionally, the results are not accurate, and parents might be told the wrong sex.