CONGENITAL ANOMALIES

Congenital means present at birth and anomaly means an abnormal deviation from the expected type, in structure, form or function. Congenital anomalies are a common cause of morbidity and mortality, especially in childhood. Many congenital anomalies are not apparent at birth although present. Unlike a cleft palate which is obvious at birth, anomalies involving the kidneys or the brain may become apparent only later in life. Aetiologic heterogeneity is a term used to describe the occurrence of similar congenital anomalies in different individuals due to different causes. To determine the cause of a congenital anomaly it is necessary to examine the family history, the pregnancy history and also whether it is an isolated single anomaly or a part of a more generalised pattern of anomalies.

TYPES OF CONGENITAL ANOMALIES

Malformations

These are morphologic defects resulting from intrinsically abnormal developmental processes. The causes are varied and have their effect early in embryogenesis. Anencephaly, polydactyly and most cleft lips are a few such examples.

Disruptions

These are morphologic defects resulting from breakdown of, or interference with, an originally normal developmental process. They arise as a result of teratogenic effects or due to unknown causes which can have an effect at any time during gestation. Amniotic band disruption is an example.

Deformations

They are abnormalities of form or position of a part of the body, caused by mechanical interference. They usually develop in the second half of pregnancy when the size of the foetus is large in comparison to the size of the uterus. Some of the factors that predispose to such anomalies are listed below.

First pregnancy
Small uterus
Uterine malformation
Large uterine fibroid
Oligohydramnios
Multifoetal gestation

Dysplasias

They are morphologic defects like haemangiomas caused by abnormal organisation of cells into tissues and usually develop during embryogenesis.

SYNDROMES AND ASSOCIATIONS

Syndromes are patterns of anomalies, all of which are pathologically related and have a similar aetiology in all affected individuals. Down syndrome and the foetal alcohol syndrome are such examples.

Associations are patterns of anomalies that occur together more frequently than expected by chance, but are not identified as syndromes. Examples are abnormal external ears and renal anomalies, vertebral, renal and cardiac anomalies appearing together.