A congenital disorder is any medical condition that is present at birth. However, a congenital disorder can be recognized before birth (prenatally), at birth, years later, or never. The term congenital does not imply or exclude a genetic cause. Congenital disorders can be a result of genetic abnormalities, the intrauterine environment, a mixture of both, errors of morphogenesis, or unknown factors. ...

A congenital disorder is any medical condition that is present at birth. However, a congenital disorder can be recognized before birth (prenatally), at birth, years later, or never. The term congenital does not imply or exclude a genetic cause. Congenital disorders can be a result of genetic abnormalities, the intrauterine environment, a mixture of both, errors of morphogenesis, or unknown factors.

A congenital disorder can have trivial or grave consequences. The most severe, such as anencephaly, are incompatible with life. Others, such as congenital tumors, vary from causing stillbirth to requiring fetal intervention to needing surgery in the neonatal period. The most common congenital tumor is teratoma. Congenital physical anomalies (birth defects) are a leading cause of death in early infancy

Causes

The cause of 40-60% of congenital physical anomalies (birth defects) in humans is unknown. These are referred to as sporadic birth defects

Genetic causes of congenital anomalies include inheritance of abnormal genes from the parents, as well as new mutations in one of the germ cells that gave rise to the fetus.

Environmental causes of congenital anomalies are referred to as teratogenic. These are generally problems with the mother. Teratogens can include dietary deficiencies, toxins, or infections. For example, dietary deficiency of maternal folic acid is associated with spina bifida. Ingestion of harmful substances by the mother (e.g, alcohol, mercury, or prescription drugs such as phenytoin) can cause recognizable combinations of birth defects.

Types

A limb malformation is called a dysmelia. These include all forms of malformations of limbs, such as amelia, ectrodactyly, phocomelia, polymelia, polydactyly, syndactyly, polysyndactyly, oligodactyly, brachydactyly, achrondroplasia, congenital aplasia or hypoplasia, amniotic band syndrome, and cleidocranial dysostosis.

Congenital malformations of the heart include patent ductus arteriosus, atrial septal defect, ventricular septal defect, and tetralogy of fallot.

Congenital malformations of the nervous system include neural tube defects such as spina bifida, meningocele, meningomyelocele, encephalocele and anencephaly. Other congenital malformations of the nervous system include the Arnold-Chiari malformation, the Dandy-Walker malformation, hydrocephalus, microencephaly, megencephaly, lissencephaly, polymicrogyria, holoprosencephaly, and agenesis of the corpus callosum.