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View our Step by Step guide to your pregnancy

Detailed Scan

The purpose of this scan is to detect abnormalities of the baby and it is normally performed at around 20 weeks. Most babies are healthy but sadly some have serious problems which almost always cannot be predicted by a family history or the health of the mother.

Approximately half of all serious congenital malformations can be detected by the 20 week scan. Thus if the baby appears normal on scan there is still a small chance that your baby will have a problem.

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 doctor carrying out your scan will be a fetal medicine specialist and thus you will have immediate access to an expert opinion.

Sometimes we cannot obtain optimal views of a certain part of the baby’s anatomy if the baby is in a difficult position. You will then be invited back for a repeat scan usually within a week so as to complete the scan.

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

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)

Problem	What we see	Chance of being detected
Spina bifida	Open spinal cord	90%
Anencephaly	Missing top of head	99%
Hydrocephalus	Excess fluid within the brain	60%
Congenital heart disease	Major heart defect	60%
Exomphalos /gastroschisis	Defect of the abdominal wall	90%
Major kidney problems	Missing or abnormal kidneys	85%
Major limb abnormalities	Shortened or abnormally formed bones	90%
Diaphragmatic Hernia	Defect of the muscle separating chest and abdomen	65%
Cleft lip and palate		80%
Down’s Syndrome	May be associated with heart, limb, and bowel problems	50%
Cerebral palsy	Severe learning difficulties	not seen
Autism		not seen