A congenital disorder is a medical condition that starts at conception or in the early stages of pregnancy. This is the residual category of the broader category of congenital defects and includes all conditions other than those relating to the nervous system (Map 12) and the heart (Map 14).

Just as with congenital heart defects (Map 14), there are wide differences between the chances of people living in different parts of the country dying due to these causes. The average age at death for this group of causes is almost 29 years but there is a very wide range around that mean. There is a north–south gradient, with Scotland and the north west tending to have higher rates, and the south of Britain lower rates.

Although these conditions start from an abnormality present long before birth, many are not diagnosed until after birth or sometimes later in life. The causes of death within this category include Down’s syndrome, which in the more recent period covered by ICD-10 (used since 2000 in Scotland and 2001 in England and Wales) account for a third of all deaths in this category. Down’s syndrome is a chromosomal disorder, which means that there is a change in the normal number of chromosomes (long strands of DNA containing all the genes). A baby normally has 23 pairs of chromosomes in every cell. In the most common form of Down’s syndrome there are three copies of chromosome number 21, instead of the usual two copies of it.

Down’s syndrome causes relatively impaired mental functioning, abnormal appearance and often congenital heart defects and other congenital disorders. Some children die before one year old from the congenital heart defects. Overall, people with Down’s syndrome have a shortened lifespan.

Down’s syndrome becomes much more common in babies born to mothers over age 35 years. Other than maternal age, no other risk factors are known. Many standard pre-natal non-invasive screening tests can detect Down’s syndrome, although all have a non-negligible chance of producing a false positive result suggesting that a foetus has Down’s syndrome when in fact it does not.