Ultrasound scans

Published by Sarah Horrocks
Published on 14 February 2008

Read up on how an ultrasound scan is performed and when you should have one.

An ultrasound scan uses high frequency sound waves to create a screen image of your womb and surrounding organs, as well as your baby, the baby’s organs and the placenta. Scans can be 2D, 3D and 4D (available privately).


How is it done?
A doctor or radiographer (sonographer) carries out the scan in hospital. You lie down, gel is spread on your belly and a handheld ultrasound probe is rolled over the area. Most obstetric departments now use vaginal probes in early pregnancy as they give a clearer picture and the results are more accurate.

Ultrasounds can be used to:

- Confirm how many weeks pregnant you are.

- Measure growth rate.

- Look for abnormalities.
- Check the internal organs are all developing correctly.
- Check the position and development of the placenta.
- Check levels of amniotic fluid surrounding your baby.
- Check the blood flow from the placenta to the baby.
- Check the position and size of your baby.
- Check heartbeat.

- Detect ectopic pregnancy.

When do you have a scan?

This varies depending on local policies and your needs. Talk to your doctor or midwife to dicuss your options.

You might be offered a scan at any of these times

- 6 - 8 weeks if you have any early pregnancy concerns, to check for ectopic pregnancies and detect the baby's heartbeat.

- 10 - 14 weeks to confirm and date the pregnancy, check for multiple pregnancies, and screen for Down's Syndrome.

- 20 - 23 weeks, your anomaly scan, to look for spina bifida and other abnormalities and to look in detail at the baby’s organs and the health of the placenta.

Later scans may be necessary if there are any concerns regarding the baby’s growth.

Are scans safe?

Medical researchers continue to monitor the long term effects of ultrasound scans, but after 30 years of use there have been no side effects noted. Studies suggest that at least one routine scan in pregnancy to confirm gestational age is valuable; however the final choice is yours. The benefits certainly far outweigh any risks.

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