The aetiology of congenital defects.

1. Big picture

Congenital defects are abnormalities present at birth, caused by disturbances in genetic programming, embryonic development, fetal growth, or intrauterine environment.

For the exam, classify causes into:

Genetic causes
+ Chromosomal causes
+ Multifactorial inheritance
+ Teratogens
+ Maternal disease
+ Infections
+ Mechanical/uterine factors
+ Unknown causes

Most congenital defects are multifactorial or unknown, not purely single-gene.

2. Definition

A congenital defect is a structural, functional, metabolic, or genetic abnormality present at birth, even if detected later.

Examples:

• Structural: cleft lip, congenital heart disease, neura