Pregnancy guide > Your baby in pregnancy > Pregnancy health > Antenatal care > Ultrasound scans - all you need to know

Ultrasound scans - all you need to know

Our ultrasound scan guide has everything you need to know about the ultrasound scans you'll be offered during pregnancy.
Ultrasound scans in during pregnancy give you the exciting opportunity to see your baby before he or she makes their way into the world and can be something of an overwhelming experience. But, despite this, many women find ultrasound scans incredibly daunting. To help reassure you we explain all you need to know about this routine procedure.

What is an ultrasound scan?

An ultrasound scan is used to produce a black and white, real time image of your baby. It allows you (and your doctor) to see both your baby's body and their movement inside your womb and is used to monitor his or her development. Most women will have at least 2 ultrasound scans during the course of their pregnancy.

Who will carry out the scan?

Your ultrasound scans will either be carried out by a specialist radiographer or by a sonographer (a specially trained midwife). They will take place either at your doctor’s surgery or at your local hospital.

When will I have an ultrasound scan?

Most women have their first ultrasound scan 10-14 weeks into their pregnancy. This is known as the 'dating scan' and is used to confirm your baby's estimated due date as in the early stages of pregnancy your baby's crown-rump length can accurately be used to reveal their developmental age. This is important as an accurate due date will help to make the results of any developmental tests more reliable (such as that for downs syndrome) and also means that your doctor is better able to monitor whether your baby's growth is on track throughout your pregnancy. The dating scan is also used to find out whether you are expecting one baby or more.

If there is a suspected problem with your pregnancy i.e. you have been experiencing bleeding or severe cramps, you may be offered an ultrasound before 10 weeks.

However, for most, your second scan will be carried out around 20 weeks. This is known as the 'anomaly scan' and is used to check that your baby is developing 'normally'. In this scan it is usual to check the diameter and circumference of your baby's head, the circumference of their abdomen and length of their thigh bone. Your baby's spine, limbs, hands, feet, internal organs and movements will also be examined using the ultrasound image.

It is usually possible to reveal your baby's sex at the anomaly scan although as this estimation isn't 100% accurate some maternity departments choose not to share this information. It is always worth asking if you want to know though and also worth mentioning to the sonographer if you don't!

If you have had problems with previous pregnancies, your baby is measuring big or small, or if you are suffering from a medical condition such as diabetes you may be offered an ultrasound scan in your third trimester. Scans in the final trimester are known as 'growth scans' and their primary purpose is to check that your baby is continuing to grow and move 'normally'.

How is the scan carried out?

When you're invited to the scan you'll be asked to wear loose, comfortable clothing and, if you are in your first trimester, to drink lots of water before the appointment as this helps to make your baby more visible in the scan as a full bladder helps to push your womb further out of your pelvis.

Once you arrive, the sonographer will apply gel to your tummy and move a transducer (a small implement that looks almost like a microphone) over your abdominal area. The transducer sends out high frequency radio waves that bounce around your baby and are sent back as echoes. It is these echoes that help to build up your baby's picture on the screen. Hard tissue such as bones is displayed in white on the image and soft tissue is displayed in varying shades of grey depending on its density. The sonographer will have been trained to interpret this image and look for signs that your baby is developing healthily.

As the quality of the image produced during an ultrasound depends on the strength of the signal produced, if you are in very early pregnancy or if you are overweight, your sonographer may suggest that you have a vaginal ultrasound instead as this will produce a much clearer picture. A vaginal ultrasound involves having a thin, lubricated, vaginal transducer (covered in a sheath) inserted a short way into your vagina. You do not need a full bladder for this scan.

Your 'dating scan' is likely to take approximately 5 - 10 minutes whereas later scans take a little longer, usually around 20 minutes as the sonographer will examine your baby's form more closely.

Will the ultrasound scan hurt?

Whether you have an abdominal or vaginal scan, having an ultrasound will not hurt at all. The only discomfort you are likely to experience is the feeling of pressure on your full bladder. The gel the sonographer spreads on your stomach can also feel quite chilly too!

Can I share my scan?

In all likelihood your partner will be able to accompany you when you have your ultrasound scans. Your sonographer will let you both see the screen and for at least part of your ultrasound and will usually point out the different parts of your baby's body so that you are able to understand the picture.

In most instances you'll be able to get a copy of the scan to take home and although it's possible that you will be charged for the picture, it can be with it to have this first image of your baby as a keepsake.

Are there any risks?

As of yet medical research has not found any risks associated with using ultrasound on either mother or baby. This is primarily because only sound waves are used to form the image and not radiation of any kind.

What will an ultrasound show?

Throughout your pregnancy ultrasound scans will be used to monitor a number of different aspects of your baby's development. These include:
  • Whether you are expecting one or more baby

  • Whether you are experiencing an ectopic pregnancy

  • Whether your estimated due date is accurate

  • Whether your baby is growing and moving as expected for their stage of development

  • Whether your baby's internal organs are developing healthily

  • Whether it's necessary for you to have further diagnostic tests because of a potential abnormality with your baby's development

What happens if an abnormality is found?

Very few developmental issues are immediately identifiable using ultrasound (although those that are include spina bifida, anencephaly and major organ or limb deformations) however your sonographer is trained to look for markers that signify whether there may be an issue with your baby's development. If a so called marker is found it doesn't necessarily mean that there is a problem but it means that potentially there could be so just in case you will be referred onto a doctor for further tests within the week. If this is the case try your best not to panic, no matter how hard this may be, as whatever the outcome of the tests there will be a plethora of information and support for you all the way.

How have you found your ultrasound scans? Were they a nerve wracking yet amazing experience? Why not share your stories or ask any questions you have in the AskBaby forums?

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