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11 Jun 2021

7 myths and facts about pregnancy scans

We look at common misunderstandings about pregnancy scans and find out what happens during a private pregnancy scan

Scans are part and parcel of pregnancy, but knowing what's on offer to you and whether you should pay for extra private ultrasound scans can be confusing.

We've asked experts from The Society and College of Radiographers and the Royal College of Obstetricians and Gynaecologists (RCOG) to debunk the myths about pregnancy scans and explain the facts.

MYTH: Ultrasound scans are 100% accurate

Routine ultrasound scans are performed at certain stages in pregnancy for a reason: because they give the most revealing or accurate results in the time frame during which they are carried out.

However, this doesn't mean all issues will be spotted or that others won't arise in your pregnancy that haven't been picked up by a scan.

Scans are carried out by humans and therefore even the best equipment in the world still has to factor in a margin for error.

And even though they spend as much time as needed carrying out all the required observations and measurements, even the most skilled sonographer might be challenged by a baby that's facing the wrong way or who won't stop wriggling.

They might also find it tricky if you're above average weight.

If you're hoping to learn the sex of your baby, this isn't always possible either. 'Sometimes it is impossible to see the fetal genitalia at the scan,' says Gill Harrison, professional officer in ultrasound at The Society and College of Radiographers.

Find out what happens during NHS ultrasound scans

TRUTH: You might have extra scans during your pregnancy

The Fetal Anomaly Screening Programme (FASP) scans are the two main ones offered in every pregnancy.

These are the dating scan - carried out between 10 and 14 weeks to take measurements and estimate your baby's due date - and the mid-pregnancy scan, which usually takes place between 18 and 21 weeks and looks in detail at the baby's bones, heart, brain, spine, face, kidneys and abdomen.

However, your individual circumstances could mean you're offered more scans. 'Further scans may be offered if there is a clinical need, for example in the case of multiple pregnancy or a low-lying placenta,' says Harrison.

Any extras that you have at private clinics, such as 'souvenir' scans, are not necessarily essential.

The first trimester: what's happening in the first 0-12 weeks?

MYTH: Pregnancy scans use radiation

While X-ray images (radiographs) are created using radiation, ultrasound scans use high-frequency sound waves to look at what's going on inside you.

The sound waves bounce between structures inside the body to present a picture of the body's internal structures - namely the baby and the mother's womb.

However, this doesn't mean it's risk-free to have as many scans as you want.

'While it is true that radiation is not used, we should not be using ultrasound without clinical need,' says Harrison.

'It's deemed to be 'safe' but there are some potential effects of ultrasound that can lead to tissue damage or problems with development, depending on factors such as the stage of pregnancy, output power of the machine and how long the scan takes, particularly if sensitive tissues are being scanned for a long time.'

You don't have to have scans if you don't want to. The NHS says: 'Some people want to find out if their baby is more likely to have a condition, while others do not. The 12-week dating scan and 20-week scan will be offered to you, but you do not have to have them.'

The choice you make will be respected and your antenatal care will continue as normal.

Should you buy or rent your own ultrasound machine?

It may be tempting to buy or rent ultrasound equipment for use at home for added reassurance or to keep an eye on what's going on in your pregnancy.

However, a joint statement by The Society and College of Radiographers and the British Medical Ultrasound Society cautions against it because repeated exposure in untrained hands could provide false reassurance of your baby's wellbeing or even cause harm to sensitive organs such as the eyes if exposure is prolonged.

Devices produced for home scans might not have the same level of control and regulatory compliance as devices approved for healthcare settings.

TRUTH: Ultrasound scans can be invasive

An external ultrasound scan is the most commonly used type in pregnancy scanning and this isn't invasive - a handheld device is run over your bump, so the sonographer can monitor your developing pregnancy.

However, in some cases you might be offered an internal ultrasound examination, too.

This scan involves a slim probe being inserted transvaginally (into the vagina) and allows the sonographer to look more closely inside the body at organs such as your womb or allow more detailed assessment of your baby.

If you are given a transvaginal ultrasound, it's most likely to be in early pregnancy - such as for IVF patients or if you have unexpected bleeding - so the sonographer can check for a heartbeat and number of babies, as well as examine the gestational sac including embryo, yolk sac and developing womb lining.

Although this type of ultrasound is invasive and may cause some discomfort, it shouldn't cause pain and it shouldn't take long to carry out.

The second trimester: what's happening in weeks 13-27?

MYTH: 3D or 4D scans are more accurate than 2D scans

This isn't the case. Conventional 2D scans are used as the gold standard at both the dating scan and the mid-pregnancy scan. Diagnostically, a 2D scan accurately gives you what you need - information about your baby's growth, how pregnant you are and if anything seems to be wrong with the pregnancy.

You don't actually need to have 3D or 4D scans apart from in some clinical settings (eg your medical team need more information about your pregnancy).

These scans are generally seen as 'nice to haves' rather than 'must haves' because they're not seen as being any better diagnostically than 2D scans.

Whereas a 2D scan is a cross-sectional view of your baby and any printout from it is black and white, a 3D scan is created taking 2D images from various angles and piecing them together. The picture from it will show the contours of your baby in colour.

A 4D scan produces a similar image to a 3D scan but also includes moving footage of your baby, plus the images are sharper and of a higher resolution.

TRUTH: You might not be able to have your partner at a scan with you during the pandemic

Restrictions during the pandemic have meant that many women had to go for pregnancy scans alone.

A small number of hospitals may still be unable to accommodate a support person for every examination due to limited space in waiting rooms, small scan rooms and inadequate ventilation.

However, NHS England and NHS Improvement now recommend that if it is safe to do so, a support person/partner can attend scans with the mum-to-be.

MYTH: You get better scans if you pay for them

In our 2021 baby survey, 72% of respondents who had private scans said they were very useful and 92% said they would recommend paying for them.

While plush surroundings and a handful of pictures, a video or even an image of your baby on a mug to take home may sound enticing, going private doesn't guarantee that the scan you're getting is any better.

In some cases (depending on where you go and the scan you opt for) they might even miss medical issues you ought to know about.

Dr Edward Morris, president of the Royal College of Obstetricians and Gynaecologists (RCOG), says the NHS ultrasound scans at around 12 and 20 weeks of pregnancy are still the safest way to monitor a baby's health and growth and to look for any potential complications.

If parents-to-be are planning a private scan it's important that they understand what type the sonographer is doing - for example, a souvenir scan without a diagnostic purpose.

'While some private scanning companies can offer a full diagnostic check to make sure the pregnancy is progressing normally, others aren't able to provide the same service and won't pick up on problems with the woman or their baby,' says Dr Morris.

'It could cause immense problems if people believe the scan will check for any potential complications when it's purely to get a good photograph. Private companies have a duty of care to ensure their customers know what type of scan they are paying for.'

In fact, there has been concern about so-called 'souvenir' or reassurance scans and how they might cause either undue worry or, conversely, miss important medical issues and give false hope.

'There are some misconceptions that everyone who does a scan is “qualified” to a similar level,' says Harrison. 'It takes six to 12 months to learn the basics of ultrasound scanning, but in some clinics sonographers have done just a one or two-day course.'

Many staff working as NHS sonographers are regulated by the Health and Care Professions Council (HCPC) or the Nursing and Midwifery Council (NMC), depending on whether they are a radiographer or a midwife, or on the Register of Clinical Technologists voluntary register.

Being registered with one of these bodies provides some protection for the public in case of incompetence or unprofessional behaviour, as well as helping to ensure a minimum standard in qualifications has been been achieved.

'Sonography is not regulated so anyone can call themselves a sonographer,' says Harrison. 'The voluntary register is exactly that - voluntary.'

Some sonographers will be eligible to join the voluntary register while others may not meet the requirements for various reasons such as level of training. However, they can still work in the UK as there is no legislation to prevent this, which is why checking relevant registers is important.

The Care Quality Commission explains that checking if someone has completed a course that's accredited by CASE (the Consortium for the Accreditation of Sonographic Education) shows that their training has at least met some basic standards.

How to get the best private scan

  • Contact the clinic before you appointment day to get information. This is so you have the chance to make up your mind whether to proceed with the scan, based on the information you receive, then find another clinic if you're not satisfied.
  • Ask them who will be doing your scan. Get their name and ask who they are registered with and what their qualifications are. You can also check if they are on the HCPC register, the NMC register or the RCT (Register of Clinical Technologists) voluntary register. The clinic should be able to provide you with this information and you have the right to be given it. If trained in the UK a CASE-accredited qualification is the kitemark for ultrasound scanning.
  • Don't be tempted to go by other people's experience. A friend's good experience may not be based on clinical judgement so don't let this sway you. The quality of the scan is what matters the most, not the 'experience'.
  • You're paying for it so ask questions. In our 2021 Which? baby survey, nearly one-fifth (17%) of the 1,000 respondents said their private scan had cost them more than they thought it would. so if you're paying for a scan, make sure it's carried out to a high standard.