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Innermost Secrets / Innermost Living / Body Clock
Skip Navigation LinksAnomaly Scans
Page modified at: 19/08/2010

Fetal anomaly scan 20-24 weeks

This is a detailed scan during which each part of the fetal body is examined. Special attention is paid to the brain, face, spine, heart, stomach, bowel, kidneys and limbs. If any abnormalities are detected the significance of the findings will be discussed and the couple will be given the opportunity to have further counselling.


20 Week Anomaly Scan
The purpose of this scan is to check development of the baby and it is normally performed at around 20 weeks. Most babies are healthy but sadly some have serious problems, which cannot always be predicted by a family history or the health of the mother. When you attend for this scan we will assume that you wish to know about all problems that are detected by the scan and any concerns that are raised. The scan is performed by a specialist sonographer or doctor. The scan is performed through the tummy wall but occasionally we may need to perform the scan through the vagina if the baby's head is low in your tummy in order to check the developing brain.

The ability to check the baby's development is dependent upon many factors. The bodyweight of the mother and the manner in which the baby lies in the womb are major issues. However, sometimes we cannot obtain what we consider perfect views of a certain part of the baby's body. In this case you will be invited back for a repeat scan. This happens in about 10% of cases so please do not be alarmed if this happens to you. You are only charged for the one visit no matter how many times we need to bring you back.

We can almost always determine the sex of the baby on scanning at 20 weeks but we will only tell you if you wish to know this information.

Over half of all serious congenital malformations can be detected by the 20 week scan. Thus if the baby appears normal on scan there is only a small chance that your baby will have a problem. This is because some problems may not be present at 20 weeks but develop later in the pregnancy e.g. diaphragmatic hernias where there is a small hole in the muscle between the lungs and the bowels.

We have a full counselling service for you should any problems be detected and we will send a copy of our report to your referring hospital, doctor or midwife to ensure good communication between all parties. This is because if we make recommendations on the scan such as a low placenta, this will need a repeat scan again later in the pregnancy to check that it has moved out away from the neck of the womb.

We check the development of the following organs or movements on the anatomy scan: head, brain, face, spine, arms, hands, fingers, heart, lungs, bowels, kidneys, bladder, legs, feet, the fluid around the baby, the umbilical cord and position of the placenta.

We have included a table of some of the problems that can be detected on ultrasound at 20 weeks and the likelihood of detection. (in part ref ; RCOG 2000)



What we see

Chance of being detected

Spina bifida

Open spinal cord



Missing top of head



Excess fluid within the brain


Congenital heart disease

Major heart defect


Exomphalos / gastroschisis

Defect of the abdominal wall


Major kidney problems

Missing or abnormal kidneys


Major limb abnormalities

Shortened or abnormally formed bones


Diaphragmatic Hernia

Defect of the muscle separating chest and abdomen


Cleft lip and palate



Down's Syndrome

May be associated with heart, limb, and bowel problems


Cerebral palsy

Severe learning difficulties

not seen



not seen