Ultrasound scans

You will probably be offered two routine ultrasound scans during your pregnancy:

1. The ‘booking’ scan – usually around 10-13 weeks.
2. At about 20 weeks – specifically, for checking your baby and the gestational age, and to provide reassurance to you that your baby appears to have no obvious structural abnormalities.

Ultrasound used to be started at about 16 weeks gestation, but with skilled sonographers and excellent equipment that’s improving all the time, it’s now possible to detect problems and take decisions about pregnancies with earlier scans.

Between 5–11 weeks an early scan can detect ectopic pregnancy and foetal heartbeats, and usually, this procedure would use a vaginal probe for the scan.

At 10-14 weeks a scan can be used to assess the risk of a baby having Down’s syndrome (Nuchal Translucency Scan). Arms, legs, face and heartbeats can also be seen.

The 11-16 week scan (Booking or Dating Scan) is used to detect the number of babies and the expected date of delivery. Fully formed arms and legs can usually be seen.

Between 18-20 weeks (Anomaly Scan) Down’s syndrome, Spina Bifida, Placenta Praevia – where the afterbirth is developing low down on the wall of the womb – and the baby’s sex can be determined. Some hospitals do not allow scan operators to tell the parents the sex of the baby in case of error.

How is it done? Is it painful?

A doctor or radiographer (ultra-sonographer) carries out the ultrasound examination in hospital. You lie on a couch, while jelly is applied to your abdominal skin – to get a better contact between the ultrasound probe and your skin – then a sound-emitting probe is moved across your abdomen to pick up the reflected sound waves for the computer generated screen picture. There’s no pain at all.

Most obstetric departments are now using vaginal probes in early pregnancy because they give a clearer image and the results are more accurate, because the probe tip can be placed closer to the uterus. The probe, which only causes a minimal amount of 'pressure' discomfort, doesn't harm the baby.