Your Ultrasound Scan

Reproduced with permission of the Royal College of Obstetricians and Gynaecologists.

As part of your antenatal care we offer to do a scan of your baby. The first scan will be done at your first antenatal visit. It is to check how many weeks pregnant you are, that there are no twins and that the baby is doing well. Usually, the scan will be through your abdomen and you should have a full bladder. Sometimes the scan will be done through the front passage (vagina) but the ultrasonographer will talk to you about this if it proves necessary.

A second scan, done at 20 to 22 weeks, is to check that your baby is normal. Most babies are healthy, but sadly some have problems which could be serious. If you really do not wish to know if the baby has an abnormality, it may be best to decide not to have this scan. If you do decide to have a scan, we will assume that you wish to know about anything that we find.

The scan will involve you lying down on a couch and a trained scan operator putting scan gel and then the scan head onto your abdomen. This will give images on the screen which allow measurements of the baby and give moving pictures. These can be difficult to see clearly, but the scan operator will try to ensure that all is well. About half of the major abnormalities that cause serious difficulties will be seen on scan and half will not be seen. This means that even if your scan is normal there is a chance that your baby will still have a problem.

The table below is a list of different types of congenital abnormality, and how likely scanning is to identify each problem.

If the scan finds a problem you will be told at the time, but a full discussion of the problem may require you to come back to hospital for a further scan and discussion with a specialist. Most problems that need repeat scanning are not serious and approximately 15 per cent of scans will need to be repeated for one reason or another. You will not be routinely offered any further scans during your pregnancy. If it is decided that you need to be scanned, the reason for this should be discussed with you. We would like to advise you that at the Ulster Hospital it is our policy not to look for the sex of the baby. You are also advised not to laminate any scan photograph as this will destroy them.

Problem	What the problem is	Chance of being seen
Spina bifida	Open spinal cord	90%
Anencephaly	Absence of the top of the head	99%
Hydrocephalus* *Many cases present late in pregnancy or even after birth.	Excess fluid within the brain	60%
Major congenital heart problems		25%
Diaphragmatic hernia	A defect in the muscle which separates the chest and abdomen	60%
Exomphalos/Gastroschisis	Defect of the abdominal wall	90%
Major kidney problems	Missing or abnormal kidneys	85%
Cerebral palsy	Spasticity	Never Seen
Autism		Never Seen
Down's syndrome	May be associated with heart and bowel problems	About 40%