A congenital disorder is a medical condition or defect that is present at or before birth (for example, congenital heart disease). These conditions can be a result of heredity or environmental factors - meaning a congenital condition could be acquired during the fetal stage of development, or as a result of the genetic make-up of the parents (or both).
A birth defect is a physical or mental abnormality present at the time a child is born.
Birth defects range from minimal, such as birthmarks, and slightly mobility-impairing, such as amelia of the legs, to very serious, such as cerebral palsy, and incompatible with life, such as anencephaly.
The majority of malformations are from unknown or multifactorial causes. About 20% of birth defects result from genetic abnormalities, and another 5% because of chromosomal problems. Others can arise from chance problems in fetal development (teratogenesis), which are sometimes caused by prenatal vitamin deficiencies or exposure to mercury and other harmful substances. Infection and disease in the mother can also cause birth defects.
About 2_3% of babies are born with congenital defects. The incidence is highest in the brain (10 per 1000 live births), heart (8 per 1000), kidneys (4 per 1000) and limbs (2 per 1000). All other defects have a combined incidence of 6 per 1000 live births.
Risk of birth defects throughout gestation
The greatest risk of a malformation occurring is between the third and eighth week of gestation. Before this time, any damage to the embryo is likely to result in fatality and the baby will not be born. After eight weeks, the fetus and its organs are more developed, and is less sensitive to teratogenic incidents.
The type of birth defect is also related to the time of exposure to a teratogen. For instance the heart is susceptible from three to eight weeks, but the ear is susceptible from a slightly later time to about twelve weeks.
Infection in the mother early in the third week may damage the heart. An infection in the eleventh week is less likely to damage the heart, but the baby may be born deaf.
- The National Library of Medicine or MEDLINE/PubMed MeSH (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=mesh&list_uids=81000151&dopt=Full) (medical subject heading) term
List of congenital disorders
Some other birth defects: