Last reviewed 01/2018

This is unknown in the majority of cases. Multifactorial inheritance is the most frequently identified cause for major malformations followed by monogenic and chromosomal disorders.

Chromosomal imbalance, the deletion and duplication of autosomes, and over 250 single gene disorders are associated with major congenital malformations. It is vital to recognise these conditions so that family counselling can take place.

Maternal illnesses contribute to approximately 3% of all major congenital malformations. Maternal diabetes, and especially the quality of its control, epilepsy and phenylketonuria are all renowned in this respect.

Drugs, X-ray radiation and alcohol make only a minimal 1% contribution to major malformations at birth.