Ultrasound scans in pregnancy: what's involved and when do you have them?

Last modified on Thursday 7 January 2021

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Ultrasound scans are a vital part of your pregnancy, helping to monitor the growth and development of your baby. From dating to nuchal to anomaly scans, here's what to expect from these particular antenatal appointments.

When you're pregnant, you'll have a lot of appointments, checks and blood tests.

But perhaps the most nerve-racking appointments you'll have are your ultrasound scans – scans that use sound waves to produce images of what's inside you.

Although the NHS describes ultrasounds as 'the safest way of looking at the developing baby without exposing the mother or baby to the risks of radiation,' the safety aspect isn't what makes them so nerve-racking.

Scans are a routine part of your antenatal care because they check for the baby's heartbeat as well as any growth and development problems throughout your pregnancy.

Although in some cases they'll reveal problems, in most cases they'll offer huge peace of mind when everything looks ok in there and are a great way to kickstart the bonding process as you get glimpses of your growing baby inside you.

To give you an idea of which scans you'll have when and what they do, we look into the key pregnancy scans offered (although some only privately). These include the following:

early pregnancy scan
dating scan
nuchal translucency scan
anomaly scan
growth scan
gender discovery scan
3D or 4D scan

What's an early pregnancy scan?

The first routine scan you'll be booked in for is your dating scan towards the end of your first trimester.

However, if you experience any unusual or worrying symptoms such as bleeding or cramping before that, you may need to have an early scan.

If an early scan is required it can take place when you're between 6 and 10 weeks pregnant.

Your GP or midwife will refer you for one at your nearest early pregnancy unit (EPU) to help rule out (or detect) early miscarriage or an ectopic pregnancy. It won't be used to detect your due date.

As you're in the early stages and the baby is very small, your scan will probably be a transvaginal scan – an internal scan that's done via your vagina, rather than over your tummy, which is known as a transabdominal scan.

What's a dating scan?

Provided there are no complications early on in your pregnancy, your dating scan will be your first official ultrasound scan.

It'll take place when you're around 10-13 weeks pregnant and you'll receive a letter confirming your appointment once you've been for your booking appointment with your midwife.

Your dating scan helps you to get a more precise idea of your due date.

It's also the first chance for you to see what your tiny baby looks like and to see and hear the heart beating.

Once you've seen everything's ok, you can breathe a sigh of relief and start sharing the happy news (unless you already have!)

Oh, and don't forget some loose change to buy a photo. NHS charges about £5 to print one out and take home.

What's a nuchal scan?

Also known as your nuchal translucency scan, this scan looks for a special measurement to detect your baby's risk of Down's, Patau's and Edwards' syndromes.

It's usually done at the same time as your booking scan if this takes place when you're 11-14 weeks pregnant.

If you're earlier on in your pregnancy than this you may need to come back a week or two later for your nuchal scan.

Find out everything about your nuchal scan here.

What's an anomaly scan?

Your 20-week anomaly scan takes place in your second trimester, anywhere between 18-21 weeks.

It's a thorough and detailed scan where the sonographer will be checking for major physical abnormalities in your baby. It can detect cleft palates, heart conditions and neural tube defects such as open spina bifida, amongst others.

This is also the scan where you can find out the sex of your baby. If you don't want to know make sure you tell the sonographer (the person doing the scan) this at the beginning of the appointment.

If she gets a clear view she'll be able to tell you whether it's a boy or a girl. However, if the baby is lying in a funny position, she may not be able to tell you at this appointment.

Find out more about your anomaly scan here.

What's a growth scan?

At your routine NHS antenatal appointments your midwife will measure your bump to help monitor the growth of your baby.

If you start measuring small or your bump is particularly large in your third trimester, your midwife may refer you for an additional growth scan.

That way, a sonographer can get a better look at what's going on inside, take the baby's measurements and check everything's ok.

What's a gender discovery scan?

Although the NHS doesn't offer a scan specifically to tell whether it's a by or a girl, these are available privately.

You may decided to have one of these if:

the sonographer at your 20-week anomaly scan couldn't tell
or, you've changed your mind about finding out the sex of your baby since having your anomaly scan.

You'll have to pay for the scan and won't be able to have it before about 16-18 weeks.

And remember, the results can never be 100% certain as it's based on what the sonographer can see during the appointment.

3D v 4D ultrasound scans

Routine NHS scans produce 2D black and white pictures. These are flat and grainy looking and not always the clearest to look at and understand.

3D and 4D scans exist and give a clearer look at your baby's features. They can also be used to get a closer or more detailed look at organs or defects, if required.

However, as the equipment is more expensive and therefore unlikely to be used in routine scans by the NHS anytime soon.

However, it is possible to access these scans and get clearer imagery at a private clinic.

Experts don't recommend having these purely to get a souvenir pregnancy photo to add to your collection. Although they're considered safe for your baby, it's also considered as subjecting your baby to unnecessary ultrasound.

But it's possible to have private scans that offer 3D and even 4D images and videos of your baby.

Find out more about having a 4D scan here.

What to expect at your ultrasound scan appointments

You'll need to drink some water before your appointment, especially at your dating scan where the baby is still quite tiny.

This helps the sonographer work out what's what and where things are as she's scanning.

You won't have to strip off for the scan. Just lie down and the sonographer will ask you pull up your top and pull down your bottoms slightly.

She'll apply some cold gel before gliding the scanner head firmly over your tummy or bump (later on in pregnancy).

It may tickle a bit but it won't hurt.

Don't worry if the sonographer doesn't talk much during it – she has to concentrate and record measurements. She'll explain things and talk you through what she's found afterwards.

You'll be told any results straight away apart from at your nuchal scan appointment where you'll get your results by letter.

If your scan does find something wrong on your scan

Could an ultrasound scan harm my baby?

The NHS states that 'there are no known risks to the baby or you from having an ultrasound scan'.

It also explains that:

'Ultrasound has been safely used for diagnostic purposes for 50 years and is an important tool in many areas of medicine.'

However, a 2010 report by the Health Protection Agency (HPA) deduced that ultrasound scans should only take place for diagnostic purposes rather than for 'souvenir' photos (such as extra scans or 3D or 4D additional scans).

It said that:

'Parents-to-be should not hesitate to continue taking advantage of ultrasound scans for diagnostic purposes.

However they should consider the uncertainties when deciding whether to have ultrasound scans that do not have a defined diagnostic benefit and provide only keepsake images or "real time" scans'.

Research has, however, found a possible link between ultrasound scans affecting whether your child is left or right-handed. But the NHS reports this as 'weak evidence' still.

Can I refuse to have an ultrasound scan?

Yes, you can.

It's your choice whether or not to have any of the scans offered in pregnancy. But although they can detect problems, they can also bring huge peace of mind if everything's well in there.

It's normal to feel nervous about the appointment so make sure you take a partner or family member along for support.

If you decide not to take up scan appointments, you will still be able to see your midwife.

According to the NHS, 'if you choose not to have the scan, your antenatal care will continue as normal.'

And you can always share your concerns or find out what other mums-to-be made of their scans in our chat forum.