Mother and Baby

Everything you need to know about your Anomaly (or 20 week) Scan

Section: Scans & Tests

It’s a mum-to-be milestone, so get clued up on what actually happens at your 20-week scan.

As pregnancy events go, your anomaly scan is up there with one of the biggest. It tends to be referred to as your 20-week scan, but can actually happen from then up until about 22 weeks, so don’t worry if yours is booked in for a bit later.

While this scan often revolves around the excitement of finding out whether you’re having a boy or girl, there are other important elements to be aware of. 

Why is it called an anomaly scan?

The only reason this mid-pregnancy scan is sometimes called an anomaly scan, is because the sonographer will be looking for any fetal abnormalities at this time. But don't worry, it's nothing to be worried about, the appointment is mainly about confirming everything spotted in your 12-week scan – so the number of babies you’re carrying and a heartbeat – as well as seeing how your little one’s developing.

What is the sonographer looking for at the 20-week scan?

Consultan obstetrician and gynaecologist Shreelata Datta tells us, ‘From 20 weeks, we can clearly see individual structures in your baby, such as his heart and brain.'

‘So, your sonographer will look at his organs and how things like his hands, tummy, face, spine and feet are forming, as well as the circumference of his head. All this can help detect certain conditions including cleft lip.’

The location of your placenta will also be checked as, if it’s lying low (placenta praevia), this can affect your birth. And of course, you can usually find out the gender of your baby!

In essence, this appointment is about confirming everything spotted in your 12-week scan

‘There’ll be a chat with whoever’s doing your scan beforehand, so you can ask any questions and tell him or her whether you want to know the sex,’ says Shreelata.

If you choose not to but change your mind later on, finding out is easier with some hospitals than others.

‘Departmental policies vary, so ask about this,’ says Shree. ‘Some ultrasound reports contain the baby's sex while others don’t, so another scan may be necessary.’

What happens during the 20-week scan?

This scan is pretty much the same as your first one (yep, you can bring someone with you and yes, you’ll need a full bladder again) although it may take a bit longer – between 30 minutes and an hour – because it’s looking at more measurements and aspects of your baby’s development.

‘Timing depends on who is doing your scan and what they’re seeing,’ explains Shree.

‘Afterwards, they’ll talk you through findings or refer you to a midwife to do that – it varies from hospital to hospital.’

More than 45,000 women have an anomaly detected at their 20-week scan each year; for advice and support, visit the charity ARC (Antenatal Results & Choices) website here

How big is my baby at 20 weeks?

Your baby is now about six and a half inches or about the size of a small cantaloupe melon. Read more about your baby at 20 weeks, including her body developments and what's going on with your pregnant body at this milestone. 

Read more:

20 weeks pregnant – what to expect


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