An ultrasound scan (sonogram) uses sound waves that bounce off solid objects to create two-dimensional black and white images on a screen. It's completely safe for you and your baby.
Scans are carried out by trained healthcare professionals called sonographers. Some midwives are also sonographers. Screening scans look for issues and check if your baby's growing well.
Three-dimensional (3D) and colour scans aren’t routinely used by the NHS.
When will I have an ultrasound scan?
You should be offered at least 2 scans:
You might also be offered a nuchal translucency scan (NT) at your early pregnancy scan to find out how likely it is your baby may have either Down’s syndrome, Edwards' syndrome or Patau's syndrome.
You can choose whether or not to have ultrasound scans.
What your ultrasound scan can show
Your scan can show:
- your baby’s size, which is important for finding out when they’re due to arrive
- your baby’s heartbeat
- the way your baby's lying in your womb, which is important when you give birth
- whether you’re having one or more babies
- how your baby’s organs and bones are developing, including their spinal cord, kidneys, bowel, brain, heart, arms, and legs
The scan can also show some health conditions and chromosomal conditions.
Scans are not 100% accurate. Sometimes there are conditions that can't be picked up by a scan.
Before an ultrasound scan
You’ll be asked to drink some water (about a pint/500 ml) an hour before the early pregnancy screening scan. Having water in your bladder will help the sonographer to see your baby more clearly.
You don't need a full bladder before the mid-pregnancy screening scan, but drinking a glass or two of water will help the sonographer.
During an ultrasound scan
Most hospitals are happy for you to have one person with you when you go for an ultrasound scan.
Young children might not be allowed to come in with you because they can distract the sonographer - it's a good idea to check beforehand.
There are a few things that happen just before and during an ultrasound:
- the sonographer will ask you to lie on a couch, raise your top to your chest and lower your skirt or trousers to your hips
- the sonographer will squeeze some gel onto your abdomen (tummy) then gently pass a hand-held device across it
- the device sends and picks up ultrasound waves that allow a computer to build an image of your baby
The scan doesn't hurt, but the gel might be a little cold at first. Sometimes the sonographer needs to press your tummy if some parts of your baby are difficult to see. The scan will take up to 30 minutes.
You should be able to recognise parts of your baby’s body on the screen – the sonographer will point them out to you.
Finding out the sex of your baby is not the purpose of the scan unless there’s a medical reason for doing so. Often it’s impossible to tell because of the position of your baby. Scans aren't completely reliable for learning your baby's sex - they can sometimes be wrong.
The vast majority of scans show that babies are healthy and no issues are found.
Finding out about a condition before birth can help parents to plan and prepare. For example, if your baby may need treatment soon after birth, healthcare professionals can help you plan to give birth in a hospital where you and your baby can have the care you’ll need.