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Pregnancy and baby

Ultrasound scans in pregnancy

What happens at a scan and what will they tell me?

Media last reviewed: 20/03/2014

Next review due: 20/03/2017

Ultrasound scans

Ultrasound scans use sound waves to build a picture of the baby in the womb. The scans are completely 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 his or her 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 you should 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 in the scan room?

Most scans are carried out by specially trained staff called sonographers. The procedure is carried out in a dimly lit room so the sonographer is able to get good images of your baby. You will first be asked to lie on a couch. You will 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 handheld device called 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 – either directly facing them or at an angle.

The sonographer will carefully examine your baby's body. Having the scan does not hurt, but the sonographer may need to apply slight pressure to get the best views of the baby.

How long will a scan take?

A scan usually takes around 20 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 is 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.

The scan can provide information that may mean you have to make further important decisions. For example, you may be offered further tests that have a risk of miscarriage.

When will scans be offered?  

Hospitals offer all pregnant women at least two 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.

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.

Some women may be offered more than two scans, depending on their health and their pregnancy. You can find out more about the dating scan and the anomaly or mid-pregnancy scan.

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 have had problems in this pregnancy or a previous pregnancy

Can I bring family or friends with me when I have the scan?

Yes. Ultrasound scans can sometimes find problems with the baby. 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 you 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.

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.

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 are offered further tests, you will be given more information about them so you can decide whether or not you want to have them. You will 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, but this depends on the policy of your hospital.

If you want to find out the sex of your baby, you can usually do so during the mid-pregnancy scan. 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 always 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.

Page last reviewed: 25/02/2015

Next review due: 25/02/2017

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