Ultrasound Scan


What is an Ultrasound Scan?

In ultrasound scanning during pregnancy high frequency sound waves are used to make pictures of the inside of your body and your baby.

Is Ultrasound safe?

Ultrasound has been used in pregnancy for over 35 years and there is no evidence that it is harmful. No radiation (X-Rays) is used.

Why do I need a scan?

There are many reasons:

  • To confirm when your baby is due
  • To check a heart beat is present
  • To identify the number of babies
  • To determine the position of the placenta (afterbirth)
  • To check the amniotic fluid around the baby
  • To monitor the growth of the baby
  • To look at the anatomy of the baby

How do I prepare for a scan?

You will need to have a full bladder for scans less than 14 weeks, but not at later stages of pregnancy.

How is a scan performed?

You will be asked to lie on a couch and a water-based gel will be applied to your lower abdomen. The ultrasonographer or consultant will move the probe over your abdomen while looking at pictures of your baby on a screen. Internal scans (transvaginal) are generally only performed in very early pregnancy.

The Dating Scan

A dating scan is performed at your booking visit at 10-14 weeks of pregnancy. During this scan we check your dates, see how many babies there are, and check that your baby appears normal.

The Anatomy (anomaly) Scan

Your consultant will discuss with you about their own policy on anatomy scans when at your first visit. The purpose of this scan is to check that your baby is developing normally.
During the anatomy scan we check:

  • The size of the baby
  • The position of the placenta
  • The fluid around the baby
  • That your baby’s head, face, spine, chest, stomach, kidneys, bladder and limbs appear normal

This is a list of different types of abnormalities or birth defects along with how likely it is that a scan will identify each problem during pregnancy

What is the problem
Chance of being seen
Spina bifida
Open spinal cord
Absence of top of head


Excess fluid within the brain*


Cleft lip


Major heart problems


Diaphragmatic Hernia
A defect in the muscle that separates the chest and abdomen


Exomphalos/ Gastroschisis

A defect in the tummy wall


Major kidney problems

Missing or abnormal kidney


Major limb abnormality

Missing bones or very short limbs


Cerebral Palsy

Spasticity, weakness of limbs

Not seen

Down syndrome

If associated with heart, bowel or kidney problems

About 50%


Not seen

*Many cases present late in pregnancy

List of Abnormalities & Birth Defects

Will a scan detect all abnormalities of the baby?

Thankfully, abnormalities are rare. Ultrasound is very good at detecting abnormalities when they are present, but will not detect them all. This means that even if your scan is normal, there is still a small chance that your baby may have a problem. If you are concerned that your baby might have a problem like Down Syndrome, the scan can look for signs of this. However, only 50-70% of babies with Down Syndrome are identified on ultrasound. It is also important to realise that ultrasound scans do not detect problems like autism or cerebral palsy. If at the time of scan a problem is suspected, you will be told. You may be asked to come back for a further detailed scan and a discussion with a fetal medicine specialist.

How many other scans will I have during my pregnancy?

The consultants will scan you on every visit and thus the number of scans will depend on the frequency of visits you have.

Can you tell the sex of the baby?

Scans can sometimes tell what sex the baby appears to be, but not always. The sex of the baby cannot be seen at the dating scan.

If I need a departmental scan can my partner attend the scan?

Yes, your partner or one other person is welcome to attend with you. Please remember the ultrasonographer needs to concentrate on the scan, and it is for this reason we ask you to limit the number of attendees. Do not bring children to the scan appointment.

Can I have a photograph of the baby?

Yes, of course, but this depends on the baby being in the right position to get a good picture.