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: 20/03/2016

Ultrasound scans

For many women, ultrasound scans are the highlight of pregnancy. It's very exciting and moving to "see" your baby in the womb, often moving his or her hands and legs.

Hospitals routinely offer women at least two ultrasound scans during their pregnancy. The first is usually when you're around 12 weeks pregnant and is sometimes called the dating scan, because it estimates when your baby is due (the estimated date of delivery, or EDD).

The second scan usually takes place between 18 weeks and 21 weeks. It's called the anomaly scan because it checks for structural abnormalities (anomalies) in the baby.

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.

Although having a scan in pregnancy is usually a happy event, be aware that ultrasound scans may detect some serious abnormalities, so you should be prepared for that information.

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 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 in several ways:

  • 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 will be adjusted according to the ultrasound measurements.  
  • To check whether you're having more than one baby.
  • To detect abnormalities. 
  • To 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. 
  • To 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).

What happens during an ultrasound scan in pregnancy?

You may be asked not to go for a wee (urinate) before you have the scan. A full bladder pushes your womb up and this gives a better picture.

You then lie on your back and some lubricating gel is put on your abdomen. A small device is then passed backwards and forwards over your skin, and high-frequency sound is beamed through your abdomen into the womb. The sound is reflected back and creates a picture, which is shown on a TV screen. 

Ask for the picture to be explained to you if the image seems confusing. It should be possible for your partner to come with you and see the scan. Many couples feel that this helps to make the baby seem real for them both. You may be able to have a picture of your baby – there might be a small charge for this.

The 20 week (anomaly) scan

This is a detailed ultrasound scan, usually carried out when you are between 18 weeks and 21 weeks pregnant. The scan checks for major physical abnormalities in your baby, although it can't pick up every problem.

The anomaly scan is carried out in the same way as the dating scan, with gel on your tummy and the sonographer passing the ultrasound device backwards and forwards. Sometimes, the sonographer doing the scan will need to be quiet while they concentrate on checking your baby. However, they will be able to talk to you about the pictures once they've completed the check. Most hospitals welcome partners into the scan room. You need to check this with your hospital.

Is it a girl or boy?

If you want to find out the sex of your baby, you can usually do so during the 20 week scan.

Tell the sonographer that you'd like to know your baby's sex at the start of the scan. 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 whether your baby is male or female.

Some hospitals have a policy of not telling patients the sex of their baby. If your hospital does not routinely inform parents about their baby's sex, you may be able to pay privately for a scan to find out. Speak to your sonographer or midwife to find out more.

Some hospitals will sell you a copy of your scan image so you can show everyone the very first pictures of your baby.

Find out more about checks and tests in pregnancy and screening for Down's syndrome

Page last reviewed: 15/01/2015

Next review due: 15/01/2017


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The 12 comments posted are personal views. Any information they give has not been checked and may not be accurate.

Swap15 said on 16 June 2014

I was 12 weeks Pregnant and was very excited for my first scan ....but unfortunately scan revealed that I had an empty Sac with no baby ...they even did an internal scan , but got same results day I was advised to go to Cotswold ward , there I came to know that formation of baby never happened and I only got empty Sac from start was a shock for me and family , as we never heard anything like this before ....I'm going through hell , both emotionally and physically....
I have done two pregnancy test one on 14th May and 24th May, both we're positive....never had any bleeding within all these 12 weeks until first scan is done nothing can be taken for sure.... I'm writing my horrible experience so that other people know how different miscarriage can be ....hope and wish no one go through all this hell....
Both nurse at Southmead antenatal clinic and Cotswold ward are really helpful .....

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Jo082 said on 22 May 2014

I'm 16 weeks pregnant, had a few bleeds, I've had no appointment for 12 week scan, I've paid for private scan to put my mind at rest, not seen a midwife yet..! Also have gestational diabetes with previous pregnancies and have not had no glucose test, a lot has changed since my first baby 15 years ago, but can never fault the care once it's there

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Skye1214 said on 29 April 2014

Does anyone know when you receive your dating scan letter?

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Lau devon said on 28 April 2014

I am 12 weeks pregnant but due to a baby boom in Devon my hospital cannot fit me in for my first scan until I am over 15 weeks pregnant. I thought I should have had it at 12 weeks so am concerned about this delay
Has anyone else had this response?
Will this have repercussions on the ability to date the bay or identify any problems?
I'm worried about the delay but perhaps it is quite normal?

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Fudge89 said on 24 July 2013

I got my appointment through for my ultrasound today. It's quite exciting as it's like an official aknowledgement of the pregnancy and I can't wait!!! My midwife isn't seeing me for the first time until a couple of days before... is this normal? Also, does anyone know the rough price to buy the ultrasound picture? And can you get more than one?

Can't wait!!!!

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Plast said on 11 July 2013

I have been told that its better to get a doctor to do the ultrasound rather than a sonographer, as the sonographer is not able to give advice like a doctor would do. plus they have to send the scan results to the GP.

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muffin86 said on 20 March 2013

're my previous post I found this site very helpful

I am also wondering why I didn't have any blood tests done as it seems that is a good way to check for miscarriage and sometimes more reliable than an ultrasound.

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muffin86 said on 17 March 2013

Why is there nothing on this page or in any of the pregnancy information given out that warns or mentions that you might not see anything in your first ultrasound and what this might mean. I am pregnant for the first time and have just had my first ultrasound. I didn't have periods before I found out I was pregnant due to the contraceptive pill. The midwife has done all my blood tests and all are fine. I went into the scan so excited expecting to be dated at around 11 weeks. I was so upset and disappointed to be told there were two sacs but nothing could be seen growing in either. I was told one is too big not to have anything in, but the other is smaller and still has a chance. I have to wait a week and go back for another scan. My partner and I were devastated and completely unprepared for this news. I had read every bit of info to prepare and inform myself about tests but not heard anything about this. Apparently I might be around 5 weeks pregnant and that's why nothing is visible, or it might be a blighted ovum. I felt so let down by my midwife and the nhs not to have been prepared for this. Everything I now know about it I have read on websites from other women who have been through the same thing. I thought if you had a positive pregnancy test, all the symptoms of pregnancy and no signs of bleeding or abdomen pain then everything must be pretty much ok. Please put something on the sight about the different things an early ultrasound might show and what this might mean. If I had been prepared it would have saved a bit of heartache. I hope any other women and their partners that are going through this find it helps to know they are not alone, and sometimes it can still work out ok. Even if it doesn't it is unlikely you did anything wrong. The egg just might never have been viable. The waiting is the worst part. Stay strong.

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Sab90 said on 14 January 2013

I am 14 weeks and 1 day, its my first pregnancy and still not had no appoinment, I understand I miss my first scan and need to know if its ok as I am worried and dont know nothing, can pple pls help me.

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lmcp1981 said on 08 December 2012

I appologise for my previous comment as I have now realised that it was you yourself that wrote the article. But having a 5 minute skim read of it I have the following comments:

In the Lorenz study the women were given weekely scans, twinty times the amount offered to NHS patients, and the ONLY side effect was preterm labour. Are we talkng a week, two weeks preterm, or more???? You don't make that clear. And may I add that the women recruited to the trial were those that were at risk of pre-term labour anyway!

The numbers in the Helsinki trial are too small to be significant are they not? Were there any other contributing factors to the miscarriages?

You didn't add the Davies trial to your reference list, however again I would question the significance of the small numbers of adverse results.

And the physiotherapist trial is irrelevant! Physios use high frequency therapeutic ultrasound to generate heat in tissues to treat scar tissue, inflammation, swelling etc. It is completely different to diagnostic ultrasound and cannot therefore be compared!

There is no critical appraisal in your article, which is incredibly dangerous in health reasearch. I refer again to the MMR fiasco!


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Susie said on 04 December 2012

Beverley - thank you for your comment. It is important to rely on the best available evidence. A systematic review of the safety of ultrasound in pregnancy was published by the WHO (World Health Organization) in 2009. The conclusion was that according to available evidence, exposure to diagnostic ultrasonography during pregnancy appears to be safe.

The WHO review references 86 studies. Anyone who would like to see the WHO review can do so via this link:

Susie at NHS Choices

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Beverley Beech said on 12 November 2012

Your web site states:
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 mother or babies and can be carried out at any stage of pregnancy.
The claim that medical research has found no known side effects of ultrasound is untrue.
Research by Lorenz showed that preterm labour was more than doubled in the ultrasound group; Saari-Kemppainen's research revealed 20 miscarriages after 16-20 weeks in the screened group and none in the controls; Davies research had 16 perinatal deaths of normally formed infants in the Doppler group compared with 4 in the standard care group; Taskinen's research found that if the physiotherapist was pregnant, handling ultrasound equipment for at least 20 hours a week significantly increased her risk of spontaneous abortion and the risk of spontaneous abortions occurring after the tenth week was significantly increased for deep heat therapies given for more than 5 hours a week, and ultrasound more than 10 hours a week.
The above are just a few of the side effects of ultrasound, I could list more, such as the Australian study that found that ultrasound reduced the baby’s weight (rather crucial in a baby considered to be small for dates!)

I trust you will amend the mis-information on your web site and I look forward to hearing from you.
Beverley A Lawrence Beech
Hon Chair
Asociation for Improvements in the Maternity Services

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