Ultrasound scans in pregnancy
Ultrasound scans use sound waves to build a picture of the baby in the womb. The scans are painless, have no known side effects on mothers or babies, and can be carried out at any stage of pregnancy. Talk to your midwife, GP or obstetrician about any concerns you have.
For many women, ultrasound scans are the highlight of pregnancy. It's very exciting to "see" your baby in the womb, often moving their hands and legs.
Having a scan in pregnancy is usually a happy event, but be aware that ultrasound scans may detect some serious abnormalities, so try to be prepared for that information.
See What if a screening test shows a possible problem? for more information on what may happen if a scan or other screening test suggests an abnormality.
What will happen at the scan?
Most scans are carried out by specially trained staff called sonographers. The scan is carried out in a dimly lit room so the sonographer is able to get good images of your baby.
First you'll be asked to lie on a couch. You'll then be asked to lower your skirt or trousers to your hips and raise your top to your chest.
The sonographer will put ultrasound gel on your tummy and tuck tissue paper around your clothing to protect it from the gel. The gel makes sure there is good contact between the machine and your skin.
The sonographer passes a probe over your skin. It is this probe that sends out ultrasound waves and picks them up when they bounce back.
A black and white picture of the baby will appear on the ultrasound screen. During the examination, sonographers need to keep the screen in a position that gives them a good view of the baby.
The sonographer will carefully examine your baby's body. Having the scan does not hurt, but the sonographer may need to apply slight pressure on your tummy to get the best views of the baby.
How long will a scan take?
A scan usually takes around 20-30 minutes. However, the sonographer may not be able to get good views if your baby is lying in an awkward position or moving around a lot.
If you are overweight or your body tissue is dense, sometimes this can reduce the quality of the image because there is more tissue for the ultrasound waves to get through before they reach the baby.
If it's difficult to get a good image, the scan may take longer or have to be repeated at another time.
Can an ultrasound scan harm me or my baby?
There are no known risks to the baby or the mother from having an ultrasound scan, but it is important that you consider carefully whether to have the scan or not.
This is because the scan can provide information that may mean you have to make further important decisions. For example, you may be offered further tests, such as amniocentesis, that have a risk of miscarriage.
When are scans offered?
Hospitals in England offer all pregnant women at least 2 ultrasound scans during their pregnancy:
- at 8 to 14 weeks
- and between 18 and 21 weeks
The first scan is sometimes called the dating scan. The sonographer estimates when your baby is due (the estimated date of delivery, or EDD) based on the baby's measurements.
The dating scan can include a nuchal translucency (NT) scan, which is part of the combined screening test for Down's syndrome, if you choose to have this screening.
The second scan offered to all pregnant women is called the anomaly scan, or mid-pregnancy scan, and usually takes place between 18 and 21 weeks of pregnancy. This scan checks for structural abnormalities (anomalies) in the baby.
When will I get the results?
The sonographer will be able to tell you the results of the scan at the time.
Do I have to have ultrasound scans?
No, not if you don't want to. Some people want to find out if their baby has problems, while others don't. The dating scan and anomaly scan are offered to all women, but you don't have to accept them.
Your choice will be respected if you decide not to have the scans, and your antenatal care will continue as normal. You'll be given the chance to discuss it with your maternity team before making your decision.
What can an ultrasound scan be used for?
An ultrasound scan can be used to:
- check your baby's size – at the dating scan, this gives a better idea of how many weeks pregnant you are; your due date, which is originally calculated from the first day of your last period, will be adjusted according to the ultrasound measurements
- check whether you're having more than one baby
- detect some abnormalities
- show the position of your baby and the placenta – for example, when the placenta is low down in late pregnancy, a caesarean section may be advised
- check that the baby is growing normally – this is particularly important if you're carrying twins, or you've had problems in this pregnancy or a previous pregnancy
Can I bring family or friends with me when I have the scan?
Yes. You may like someone to come with you to the scan appointment.
Most hospitals do not allow children to attend scans as childcare is not usually available. Please ask your hospital about this before your appointment.
Remember, an ultrasound scan is an important medical examination and it is treated in the same way as any other hospital investigation. Ultrasound scans can sometimes find problems with the baby.
If everything appears normal, what happens next?
Most scans show that the baby is developing normally and no problems are found. This is because most babies are healthy and do not have abnormalities. You can continue with your routine antenatal care.
If the scan finds there might be a problem, what happens next?
If a problem is found or suspected, the sonographer may ask for a second opinion from another member of staff. You might be offered another test to find out for certain if there is a problem.
If you're offered further tests, you will be given more information about them so you can decide whether or not you want to have them. You'll be able to discuss this with your midwife or consultant.
If necessary, you will be referred to a specialist, possibly in another hospital.
Is it a girl or a boy?
Finding out the sex of your baby is not offered as part of the national screening programme.
If you want to find out the sex of your baby, you can usually do so during the mid-pregnancy scan but this depends on the policy of your hospital. Tell the sonographer at the start of the scan that you'd like to know your baby's sex.
Be aware, though, that it's not possible for the sonographer to be 100% certain about your baby's sex. For example, if your baby is lying in an awkward position, it may be difficult or impossible to tell.
Some hospitals have a policy of not telling patients the sex of their baby. Speak to your sonographer or midwife to find out more.
Can I have a picture of my baby?
You will need to check if your hospital provides this service. If they do, there may be a charge.
Media review due: 5 April 2020
Page last reviewed: 30 November 2017
Next review due: 30 November 2020