The probe sends out ultrasound waves – sound waves with a frequency higher than the human ear is able to hear – to produce images of your baby, which the sonographer studies on a screen.
Ultrasound scans in pregnancy have several purposes:
Ultrasound scans have been used for many years, and there are no known risks to you or your baby from having the routine scans offered in pregnancy.
If you’re considering a private 3D or 4D scan, it’s worth considering that these scans often last longer, meaning your baby will be exposed to more ultrasound than they are during routine scans.
While there’s no evidence to suggest that this is unsafe, it’s recommended that non-medical scans are avoided in the first 10 weeks of pregnancy, as the embryo is potentially more vulnerable at this early stage, according to a .
All pregnant women in England, Scotland, Wales and Northern Ireland should be offered at least two ultrasound scans on the NHS as part of their , known as the Fetal Anomaly Screening Programme (FASP).
You might be offered more than two scans – for example, if there are concerns about your health or your baby’s growth. But for most women having straightforward, healthy pregnancies, the early pregnancy scan and the anomaly scan are all that are recommended.
Taking place between 8 and 14 weeks, the early pregnancy scan, or dating scan, is your first pregnancy ultrasound. This scan will be done as a black and white 2D scan.
The dating scan will establish how far along you are and give you an estimated due date. It will check whether you’re expecting one baby or more and that your baby is developing as it should be at this stage.
You should also be offered an antenatal screening test for Down’s syndrome and other chromosomal abnormalities at this stage. This is called the combined test, because it involves a blood test as well as the scan, and can be carried out between 10 and 14 weeks. It’s also sometimes referred to as the NT (nuchal translucency) scan.
The test can’t tell for sure whether your baby has Down’s syndrome or another similar condition but can identify whether they’re at risk. It takes up to two weeks to get the results, but you should be told within three working days if your baby is at high risk. Based on the result, you might choose to have further tests to get a definitive answer.
If you’d rather not know about possible risks, you can have the dating scan without the combined test. Talk to your midwife about how to arrange this.
Between 18 and 21 weeks, you’ll have your anomaly scan, which is sometimes called the mid-pregnancy scan.
The sonographer will take a detailed look at your baby’s heart, brain, bones, spinal cord, face, kidneys and abdomen to check for a range of conditions. Not all problems can be detected by the anomaly scan, but if the sonographer sees any cause for concern, you’ll be told there and then. This is also done on the NHS as a black and white 2D scan.
This traditional scan - which you get on the NHS - creates a cross-sectional view of your baby, producing outlines rather than a 3D rendition. If you get a printout from this type of scan it'll be black and white, flat-looking and you may need some help in interpreting what you see.
While this might not sound that thrilling from an 'experience' point of view, diagnostically it is highly accurate when it comes to growth assessment, checking amniotic fluid and looking for the majority of birth defects. You can also find out the sex of the baby from this kind of scan if you wish - and if your baby is in the right position.
A trained sonographer will gather good information from this scan, including skeletal make-up and internal organs (including brain development), and they'll be carrying out lots of different measurements while you're being scanned, many of which you might not even be aware of.
As well as the routine NHS scans, there are several different types of private scan that you might choose to have. Unless you are having entirely private antenatal and maternity care – in which case your two Fetal Anomoaly Screening Programme (FASP) scans are likely to be carried out by your private team rather than the NHS – these private scans are nice-to-haves rather than must-haves.
Pregnancy scanning as early as six weeks isn't generally carried out on the NHS and the Royal College of Obstetricians and Gynaecologists (RCOG) recommends that scans shouldn't be carried out before 10 weeks gestation unless they are clinically indicated.
However, if you want a scan this early to see whether your pregnancy is developing normally, you could go for a private 'viability scan'. You’ll see a beating heart, and if you have the scan towards the 10-week mark you can also see the baby’s head and where the limbs are forming.
This scan can be reassuring if you’ve had a previous miscarriage or are feeling very worried, or you may be given one if you've had fertility treatment.
However, it’s important to note that if you experience any problems like pain or bleeding early in your pregnancy you should always contact your GP, midwife or the Early Pregnancy Assessment Unit (EPAU) first.
They might be able to give you a scan without you having to pay to have it done privately and also do other checks to make sure you and your baby are healthy.
A viability scan can either be performed transabdominally (on the surface of your tummy) but if your pregnancy is in the very early stages, you might be offered a transvaginal scan using an internal probe.
Sonographers can usually tell you the sex of your baby at your NHS anomaly scan at around 20 weeks. However, sometimes it’s not possible to tell the sex at that scan as your baby might be in a position that makes it difficult for the sonographer to see, in which case you may want to have a private scan to find out the sex later on.
If you’re really keen to know the sex of your baby, you can have a private gender scan from as early as 16 weeks. However, the further on in your pregnancy you are, the easier it is to get an accurate idea of whether it's a girl or boy.
This type of scan is performed transabdominally (occasionally transvaginally) from 11 weeks to around 14 weeks and, amongst other things, is used to assess the chance of Down's syndrome and other chromosomal abnormalities. It will be given to you on the NHS if there is a clinical reason for offering it to you but you can also pay for one.
You will be given an estimate of your individual chance of these for this pregnancy and it is calculated by taking into account maternal age, the measurement of two hormones in the mother's blood and the scan findings of nuchal translucency thickness, the nasal bone, blood flow through your baby's heart and any abnormalities detected.
Along with the diagnostic testing, you should also receive full counselling concerning the significance of these chances, as well as options for further investigations.
In the second half of your pregnancy, you can get a really clear view of your growing baby through a private 3D or 4D scan.
You should also be able to find out the sex, and usually get a selection of pictures or, in the case of 4D scans, video to take home.
The best time to do a 3D or 4D scan is usually towards the end of your second trimester or at the start of your third trimester (around 26-32 weeks). Before 26 weeks your baby hasn’t put on a lot of fat and so will look very skinny and the bones of the face will show through.
After around 32 weeks your baby is more squeezed up and running out of space in the womb, so it’s harder to get clear pictures.
A 3D ultrasound is created by taking 2D images from various angles and piecing them together. These tend to be offered by private establishments as part of 'souvenir' packages rather than for medical diagnostic purposes. With 3D you can see the contours of your baby's face, including their mouth and nose, and you might even see them yawning, moving or poking their tongue out.
Before you have a 3D (or, indeed, a 4D) scan, think about whether you actually want to see this level of detail – some parents-to-be like what the baby looks like to be a surprise for when they are born.
There are few clear medical benefits of 3D over 2D, and experts say they should only be done if there's a medical need (some NHS fetal medicine units have 3D scanners but only for use if it's medically necessary).
For example, showing the extent of spinal lesions or skeletal disorders and seeing the detail of the brain, where there is suspicion that something is not as it should be.
Diagnostically, 3D images may enable sonographers to further assess some abnormalities that could be trickier (though not impossible) to examine in 2D, such as cleft lip.
Some researchers have suggested that they can also be useful in explaining any abnormalities to parents, who may be better able to visualise what's wrong with a 3D image than with a 2D one.
If you want a 3D scan you will most likely have to organise it privately and because of the cost of the equipment and software they are expensive.
Diagnostically, both 4D and 3D scans enable you to look at your baby's features more closely, but with a 4D scan you get video footage and not just a still photo.
Depending on the type of scan you have e.g. diagnostic (to look for potential malformations) or ‘social’ (to see the baby) they may also more easily pick up issues such as musculoskeletal malformations, problems with facial development such as facial clefts, issues with the hands and feet, as well as subtle abnormalities that aren't necessarily seen in 2D.
Additionally, the sonographer will be able to check growth, the position and appearance of the placenta and the amount of amniotic fluid.
Also, being able to digitally store the scan also enables a medical team to reload the files and examine them after the event, allowing for even closer inspection of the foetus even when the appointment is over. If you want a 4D scan you're likely to have to pay for one privately.
The same applies for 5D scans, which have sharper images and a higher resolution than 2D, 3D or 4D.
The price you’ll pay for non-NHS scans depends on the type of scan you want, how many private scans you have and the area you live in.
A survey we ran in 2019 showed that while 18% of people who had private scans paid less than £50, 10% of parents spent more than £500.
There are a range of reasons you might choose to have private scans in addition to the standard two NHS ones, including reassurance, to find out your baby's sex or to get photos or video footage of them inside your womb.
According to our survey of parents in 2021, 30 per cent paid for a private scan. Reasons for choosing to go for a private scan included wanting a 3D scan, a 4D scan or being scanned because they were having IVF.
The coronavirus pandemic was also a factor. Our survey showed a higher number of people who had babies during the pandemic paid for private scans (36%) compared to those who had babies outside of the pandemic (29%). Being able to have their partner at the scan with them when this was restricted in the NHS was cited as a reason for going private.
The advice from the National Institute for Health and Clinical Excellence (NICE) is to have your early scan and then the anomaly scan at 18-20 weeks. Feeling anxious about your baby is quite natural during the early stages of your pregnancy and if you have any concerns you should consult your midwife first.
If a scan reveals a possible problem with your pregnancy or baby, the sonographer might ask for a second opinion from another professional. This might be done straight away or you may have to come back for another scan.
You might be offered further tests to give you more information about the problem, but you won’t have to make an instant decision about whether to have them. You’ll be able to discuss it with a midwife or doctor who can explain what’s involved and, in some cases, you might be referred to a specialist.
It’s always upsetting if antenatal screening tests or scans uncover a problem, but support is available from doctors, midwives or specialist support groups.
The charity , which stands for Antenatal Results and Choices, can provide information and support. It has extensive online advice and a helpline that you can call to help you understand the information the midwives and doctors have given you and make the right decisions for you and your family.
The Royal College of Obstetricians and Gynaecologists (RCOG) says that attending antenatal care, such as routine scans, when you are pregnant is essential to ensure the wellbeing of you and your baby.
If you are well and have no complications from past pregnancies and are due a routine scan, you should be able to attend as normal and your partner should be allowed attend with you but you may want to check with your maternity team to make sure this is the case.
If you are in self-isolation and have an antenatal appointment coming up, you should contact your midwife or antenatal clinic to inform them of your situation.
It’s likely that your routine appointments will be delayed until your isolation period ends. If your maternity team advise you that your appointment can’t wait, the necessary arrangements will be made for you to be seen.
If you have suspected or confirmed COVID-19, you should also contact your maternity team and they’ll arrange the right place and time for you to attend your appointments: you should not attend a routine clinic.
If you have any concerns about the wellbeing or yourself or your unborn baby during your self-isolation period, contact your midwife or, out of hours, your maternity team for further advice on whether you need to attend hospital or not.