Are ultrasound scans safe during pregnancy?

When you’re pregnant, ultrasound scans are a routine part of your care - as they monitor the development of you baby within the womb.

So, they are a common and accepted part of pregnancy. But you may worry about ultrasound scans, particularly when it comes to the safety of you and your baby. And you may have questions about them, such as:  What exactly are ultrasound scans? Are ultrasound scans safe? Can they harm you or your baby?   

To help you, we are going to answer these questions about ultrasound scan safety – and many more – in this guide.

What is an ultrasound scan?

An ultrasound scan, also known as a sonogram, is a medical imaging technique that uses high-frequency sound waves to produce an image of the inside of your body. In pregnancy, the role of ultrasound scans is to monitor the development and growth of an unborn child. But they are also used in other ways – for example to guide surgeons during operations, and to help diagnose certain conditions.

How ultrasound scans work

Ultrasound scans work through an ultrasound sensor, which emits high-frequency sound waves that bounce off parts of your body. These sound waves are then picked up by the sensor, which turns them into the images that you can see on a monitor during your scan.

How many ultrasound scans will I have during my pregnancy?

You will be offered at least two ultrasound scans during your pregnancy. These are your early pregnancy scan, that will take place between 11 and 14 weeks, and your mid-pregnancy scan, also known as the foetal anomaly scan, which happens between 18 and 21 weeks.  At the earlier scan, you may also be offered a nuchal translucency scan. This is an ultrasound scan that measures the clear space in the tissue at the back of your baby’s neck, known as the nuchal fold. When combined with a blood test this assesses the chances of your baby having Down's syndrome, Edwards' syndrome or Patau's syndrome.

It's possible that you may be offered more scans if your doctor is concerned about your health or your baby’s, or both.

Why are ultrasound scans in pregnancy important?

Ultrasound scans in pregnancy provide valuable information about the health and development of your baby, such as:

• The number of foetuses, to reveal if you’re expecting more than one baby
• The size of your baby, which is important for predicting your due date
• How your baby is lying in the womb, which is important in regard to planning your delivery
• The development of your baby’s organs and bones, which enables some problems to be spotted early
• The position of your placenta, which is the organ that passes nutrients, antibodies and oxygen to your baby in the womb.  This is important because if you have low-lying placenta – for example – you may be advised to have a caesarean section
  

What type of ultrasound scan will I have?

You’ll have what’s called a transabdominal ultrasound scan. This is the most common type of ultrasound scan, where you have gel rubbed onto your tummy and then a hand-held sensor is moved over your skin. You’ll be able to see a picture of your baby on the screen. The sonographer will measure your baby to see if it matches the right size for your dates. This may lead to a new estimated due date.

How long will each ultrasound scan take?

An ultrasound scan usually takes between twenty to thirty minutes. However, it may take longer if your baby is lying in an awkward position, as the sonographer may not be able to get a good enough view. If it's proving really difficult to get a good image, then you may be asked to book another appointment, so the ultrasound scan can be done again.

When will I get the results of my ultrasound scan?

For most scans, your sonographer will discuss the results with you during your appointment. However, if you have the nuchal translucency scan, the results need to be combined with your age and blood test measurements - so you could have to wait for up to 2 weeks to get the results.

Are ultrasound scans safe for me and my baby? Are there any risks involved?

Ultrasound scans in pregnancy are safe. Multiple studies have shown there is no risk to mother or baby from ultrasound scans.

You may read some worrying things online about the potentially harmful effects of ultrasound. But remember that, when you visit the hospital, your ultrasound scans will only be performed by trained healthcare professionals who know exactly what they are doing. So, there is nothing to be concerned about.

Do I have to have an ultrasound scan in pregnancy?

No – it is your decision and, if you decide not to have ultrasound scans after discussing it with your medical care team, that choice will be respected and it will not affect the rest of your care. Some people choose not to have scans as they don’t want to know if their baby has a condition.