Antenatal Screening

18-20 week antenatal scan (low risk results)

All women will be offered a dating scan, and an 18- 20 week fetal anomaly ultrasound scan, in line with NICE and UK National Screening Committee recommendations. 

The purpose is to check the baby is developing as expected and to look for any serious abnormalities, such as heart problems, spina bifida or chromosomal conditions such as Edwards’ syndrome and Patau’s syndrome. This can help parents decide whether to continue the pregnancy. It can also identify problems that may benefit from early intervention following delivery and in some cases interventions that can be carried out during pregnancy. 

Most people we talked to were broadly aware of this purpose. Some of them felt very well prepared, while others would have liked more detailed information about what the scan looks for.

All pregnant women should now be given by their midwife or GP the booklet ‘Screening tests for you and your baby by Public Health England, which gives detailed information about the types of scan offered and what they are looking for (see NHS Choices or 'Resources' section).

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One woman who had a scan in California felt her doctor in the UK explained it better. Another suggested the person doing the scan should check that the woman was properly informed. She noted that some scan technicians do a quick check for themselves before turning the screen round to face the woman, which may be a sensible precaution in case something is wrong. (See also below).

Some people saw the 18-20 week scan as somehow different to screening, and some felt it would be too late by that stage to consider ending the pregnancy if anything were wrong with the baby, although in fact terminations for severe abnormality can legally be carried out at any stage of pregnancy.

Of course for the great majority of people, the 18-20 week scan reassures them that their baby looks fine. Women described many positive aspects, including the joy of seeing the baby and having a photograph; feeling closer to the baby and making the pregnancy seem real (especially for partners); and sometimes finding out the baby's sex, although this is not always possible or permitted.

One woman who had to have an internal scan (using a vaginal probe) because of the baby's position found this did not spoil her enjoyment of the scan. For some people, having to have a full bladder, especially if the person doing the scan then pressed hard on their abdomen, was a minor drawback. Two people mentioned they had heard that the sound waves in a scan may distress the baby, but there is no conclusive evidence for this.

Although most people said scans had made the pregnancy seem more real for their partners, for one father it was buying baby clothes that suddenly made it feel real. One mother felt the 18-20 week scan was an anti-climax after having seen the baby before. A few commented that the quality of the pictures was poor, but other people were impressed by the quality. This may depend on the type and age of equipment being used.

A very important concern for people was the way the person doing the scan communicated with them. Some people could compare different experiences; one woman had a senior consultant the first time, who was expert but brief, whereas the second time the scan was performed by a specialist midwife who recognised what an important emotional experience this is for parents.

Some sonographers talk throughout the scan, explaining what they are looking at and whether it is normal. This approach was preferred by virtually everyone we spoke to, including a French woman and her British partner who had their scan in France. She came away reassured, but also well informed that the scan could not guarantee there were no problems that would be discovered later.

Staff who are talkative during a scan may suddenly go quiet if they notice something unusual, and this can create anxiety. Some staff chose instead to remain silent while they concentrated on the scan, but explained beforehand this was what they would do. Most people we talked to still felt they would rather know immediately if staff had seen something unusual.

An anxious moment was described by a woman with previous experience of a scan which found the baby had died. She would have preferred a more immediate explanation.

One person thought it must be difficult for staff to check if there is something they are not sure about if the woman is watching throughout, which has become more common since she had her first scans some years ago.

A few staff did not explain they would be silent, and this made some people quite anxious. This is discussed further in the '18-20 week scan (being told something may be wrong)'.

Lack of communication was sometimes more to do with pressure of work. One woman felt staff did not have much time to communicate properly and came away anxious that something might have been missed.

Although some people had gone to the 18-20 week scan alone, most felt it was important to have someone with you for support, in case something unusual was detected. Two women said their partner had missed the scan because they were still trying to find a hospital car parking space.

Many experiences discussed here are common to other types of scan - see also  'Early dating scans' and 'Combined screening for Down's syndrome and other chromosomal abnormalities'.

For further information on screening tests please see our pregnancy resources. 

Last reviewed July 2017.
Last updated July 2017.


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