Imaging (Scans), Sports & Exercise Medicine, Obstetrics & Gynaecology, Neurology, Radiology


Introduction to Ultrasound

An ultrasound scan may be required prior to 10 weeks of pregnancy. To perform a vaginal ultrasound your sonographer will coat a slim, smooth probe with lubricant and gently insert it into your vagina. It is completely painless although may feel a little uncomfortable. Your gestation measurements will be taken and your due date predicted.

Written by Doctify Team 27/04/2020

What is an Ultrasound?

An ultrasound scan is a procedure, where a machine produces high-frequency sound waves to create an image on a screen showing the inside of your body. They are most commonly used to view babies inside the mother’s womb, but can also be used to diagnose many other conditions and to help guide surgeons during operations. Thousands of ultrasound scans are carried out each year, they are painless procedures and are not known to carry any risks.

How is an Ultrasound performed?

A small device called an ultrasound probe is used; this probe emits high-frequency sound waves. The frequency of these sound waves is too high for the human ear to hear these sound waves, but when they are reflected off different parts of the body, they create ‘echoes’ that are then picked up by the probe and turned into a moving image that is displayed on a screen during the scan. The scan can take anywhere from 15-45 minutes.

How to prepare for an Ultrasound?

Before the scan, the doctor may ask you to drink water and not go to the toilet. This is because a full bladder helps improve the quality of the image during that scan. If you are having a scan of your digestive system you may be asked not to eat before the scan. Depending on the area being scanned, you may be asked to remove your clothing and wear a special hospital gown.

What happens after an Ultrasound?

You can usually go straight home after an ultrasound scan. You may be told the results of the scan as soon as it has been carried out, but sometimes the images need to be viewed by a specialist doctor, called a radiologist who will write a detailed report on the images. If you are having a scan of a baby, you can usually get print outs of the images and sometimes even a movie of the scan. A doctor who specialises in maternity medicine, called an obstetrics and gynaecology doctor, will be able to give you further information on the ultrasound scan procedure.

Different types of baby scans

1. Dating scan (12-week scan, booking scan or due date scan)

At 12 weeks you will be able to see more detail and make out hands and feet. With a few exceptions from 10 weeks of pregnancy, you would normally have an abdominal ultrasound. You will be asked to drink a pint of water approximately an hour before the scan and will need to come to the appointment with a full bladder. This makes it easier for the baby to be seen clearly. Your sonographer will rub some jelly onto your stomach and use a small probe to gently press on your abdomen. A vaginal ultrasound may be necessary if you are overweight or your baby is deep inside the womb.

2. Nuchal Translucency (ultrasound NT scan, NT baby scan) 

You would normally see your baby at an NT scan, although the purpose is Nuchal thickness measurement. Combined with your blood test results and your medical and family history the results are 80 to 85% accurate at determining chromosomal abnormalities. Dependent on where you are having your ultrasound NT  scan, results will normally available between 1 and 3 days after your appointment.

3. Morphology scan (detailed ultrasound scan)

An ultrasound scan between 18 and 22 weeks will give you more detailed images of your baby. The level of detail you will be able to see will depend on whether you have, a 2D or 4D baby scan. 

4. Presentation Scan (baby weight scan, baby size scan)

This scan will show you tiny details, such as your baby’s fingernails. Facial features will be clear and you may even see your baby blinking. Placental circulation assessment will be carried out to predetermine any possible complications. Your baby’s length and weight will be estimated to give you a good idea of how big your baby will be when born.

When can I find out the sex of my baby?

Although it may be possible to tell the sex of your baby at an early scan your sonographer will be reluctant to commit. From 10 weeks onwards it will normally be possible to tell the sex of your baby. You can ask you sonographer to try not to show you the sex or tell you the sex of your baby if you would prefer it to be a surprise. 

How long does an ultrasound take?

On average, an ultrasound will last for approximately 15 minutes. You should allow 45 minutes to give you time to sign any forms. 

What is the difference between a 2D scan and a 4D scan?

Standard ultrasound machines only show a 2D image on the screen. The image will be black and white and fuzzy. You will be able to see your baby’s body and your sonographer will point out the head. You may also be able to see your baby’s sex, dependent on how far you are gone and the angles of the images. 

  • 6 to 11 weeks Viability scan (early scan or first scan) 
  • 10 to 13 weeks Dating scan (12 week scan, booking scan or due date scan) 
    Nuchal translucency scan (ultrasound NT scan, NT baby scan) an be done separately or combined with dating scan
  • 18 to 22 weeks Morphology scan (detailed ultrasound scan)
  • 24 to 36 weeks Presentation Scan (baby weight scan, baby size scan)

How does Ultrasound (sonography) work?

An ultrasound scan uses a probe (transducer) to transmit, millions of high-frequency soundwaves into your body. The harmless high-frequency inaudible sound waves bounce back to the probe and this is how the image is created on the screen, in real-time.

What happens in an ultrasound scan and what are the risks?

An ultrasound baby scan can be done externally by running a probe over your abdomen or internally using a vaginal probe. This is completely painless and the sonographer knows how and where to press to avoid causing the baby any distress. An ultrasound (sonogram) scan is totally safe for both you and your baby. You will be able to hear your baby’s heartbeat and beside you will be the screen where you will see images of your baby. Your sonographer will be able to give you any information you have agreed prior to the appointment that you want to know. 

Will I see my baby’s face on a 4D scan?

  • At around 12 weeks you will be able to make out some facial features 
  • Between 18 weeks and 22 weeks, you will be able to see minute details, such as your baby’s blinking and yawning

When can I have a 4d scan?

You can have a 4D scan at any time after 10 weeks. Most woman will have 2 one around 12 weeks and one between 22 and 24 weeks. 

Where can I have a 4d scan?

Almost all private scanning centres now have 4D ultrasound scanners. Many offer packages if you want more than one scan. Most will also offer additional tests, to check if your baby has any developmental abnormalities.

  • Ultrasounds are most commonly used to view babies inside the mother’s womb
  • An ultrasound (sonogram) scan is totally safe for both you and your baby
  • On average, an ultrasound will last for approximately 15 minutes
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