Ending a pregnancy for fetal abnormality

The 18-20 week antenatal scan and further tests

The 18 -20 week fetal anomaly scan is a watershed in most pregnancies because for the majority of women it will be the last time they are scanned before giving birth. Some people we talked to had not had a 18-20-week scan, either because their babies' abnormalities had been detected by earlier diagnostic tests (e.g. the amniocentesis) and the pregnancy had already ended, or because the scan was not routinely offered in their region 5 or more years ago.

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

For many other women, the 18-20 week scan was the point at which they discovered the baby had serious problems. 

18-20 week scans provide clinicians with more information than earlier scans because by 18 weeks a healthy baby should be larger and better developed. Health professionals use the 18-20 week scan to examine the baby's size and position, and also to check if his/her brain, heart, lungs and other internal organs are developing as expected.  

Severe chromosomal conditions such as Edwards' syndrome are now often picked up in the first trimester antenatal screening but it will usually be more obvious at the 18- 20 week scan, though usually a firm diagnosis will not be made until one or two specialists have weighed up all available evidence about the baby - which usually means that another expert needs to scan the baby again, or until the woman has had an amniocentesis.  

Sometimes women were told that the sonographer had found a 'marker' or sign of a chromosomal condition and had to wait for an amniocentesis to confirm the findings. (See 'Resources').

The Royal College of Obstetricians and Gynaecologists (RCOG) have produced a report on ‘Termination of Pregnancy for Fetal Abnormality in England, Scotland and Wales’ (May 2010).

Within it are a number of recommendations for the communication of findings from ultrasounds. The following is a quote from their report:

“If the scan reveals either a suspected or confirmed abnormality, the woman should be informed by the sonographer at the time of the scan. It is essential that all practitioners performing fetal anomaly ultrasound screening should be trained to communicate abnormal findings to women, as such information is likely to have significant emotional impact.

Usually, sonographers will ask a senior sonographer colleague to confirm findings and this should be done immediately. If an abnormality is confirmed or suspected, referral is usually required, although some obvious major fetal abnormalities, such as anencephaly, may not require a second opinion (this should be decided by local guidelines).

For women who have been given distressing news about their baby during the scan, there should be a health professional available to provide immediate support. In the case of a suspected abnormality, women should be seen for a second opinion by an expert in fetal ultrasound, such as a fetal medicine specialist. An appointment should be arranged as soon as possible and ideally within three working days. Any delay in receiving more information about the abnormality and its implications will be distressing for women and this should be acknowledged.

Limitations of the 18-20 week scan

Though the 18-20 week scan can detect when certain parts of the baby's body have grown abnormally, it may not be possible for clinicians to identify why it has happened or make a firm diagnosis based on the scan alone. Sometimes doctors will wait to give the baby more time to develop and carry out repeat scans - this had confused several parents we talked to who had gone for repeat scans not knowing that the baby might have a problem. For instance a couple who knew their baby was 'on the small size' were told he was fine at the 18-20 week scan, but discovered at 32 weeks that he had microcephaly.  

Some parents wondered if it was possible to have the same scan done at 16 weeks rather than 20 weeks. Some hospitals do offer earlier anomaly scans of the baby, but they will not show as much detail as scans performed between 18 and 20 weeks.

Sometimes a post mortem was needed to confirm the 20-week diagnosis to see if the baby had inherited a genetic problem (such as Fowler syndrome - see 'Resources')

Specialist scans

Sometimes specialist scans such as 3D scans, or MRI scans, are used to examine the baby in greater detail. Specialist scans are performed in specialist fetal units and if clinicians feel that there might be problems scanning will be done up to 32 weeks.

Specialist scans had a powerful effect on some parents because they could see the baby more clearly and in some cases people recognised which parts of the baby's body were not working properly.

Impact of the 20-week and later specialist scans

Many parents were shocked by findings from the 20-week and later scans. Some people had underestimated how serious any abnormality found at this stage could be for the baby. Others, including those who had been given leaflets to read about the scan beforehand as well as some who were health professionals, said that they had been naïve about the 20-week scan.  Several women had taken young children with them to the 20-week scan because they expected to see 'nice pictures of the baby'.  

Others said they were shocked because all the early diagnostic tests (e.g. blood tests, CVS) were clear - and as one woman put it, 'after the triple test* (Down's syndrome screening) you stop thinking anything can go wrong'.  

All pregnant women should be given the booklet by their midwife or GP ‘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.

Many people were deeply affected by their experiences of the 20-week and subsequent specialist scans. Many described how sonographers and doctors were very restrained and didn't speak at all until they had analysed all the baby's details. While some parents understood the clinician's restraint - even when they had to wait an hour or more for a definite diagnosis - others disliked being kept in suspense and wanted to be told what the clinician was thinking. Several parents said they would have preferred being told something, even it was vague. 

A few people recalled how frightened and alarmed they became when they sensed that the atmosphere in the scanning room changed in an instant from 'jokey' to serious when the baby's problems were detected.


*The triple test (blood test) is now no longer offered as a screening test and the quadruple test does not give a risk assessment for neural tube defects. Spina bifida is now more commonly diagnosed during the ultrasound scan carried out around week 12 of the pregnancy or, more likely, during the anomaly scan carried out around weeks 18 to 20.

Last reviewed July 2017.
Last updated July 2017.

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