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Birth defects are abnormalities that are present when a baby is born. This is a rather old-fashioned phrase that has continued to be useful in medicine and in popular culture, although it certainly both perjorative and somewhat misleading. Some of characteristics that are properly called "birth defects" are not particularly consequential, and may not have much (or any) real negative value for the baby - and so, defect is a rather unfortunate part of the term. Further, some things that are properly though of as birth defects are rarely discovered at birth - but manifest in later childhood or even adulthood.
Still, this term for congenital anomalies is not only - in the main, descriptive, but conveys the type of health problem in a succinct way that no other phrase has managed to yet replace. Birth defects most often occur during the development of a baby, and are the consequence of many possible causes.
- Some, like the lack of limbs in babies born to mothers who took thalidomide during early pregnancy, are from exposure of the baby to toxins. Fetal Alcohol Syndrome is one of the most common birth defects that occurs from that kind of problem.
- Others, like Down Syndrome, are the result of an abnormal number of chromosomes. That is called anupleudy and, depending on which chromosomes are either extra or missing, can range from such a severe spectrum of abnormalities that the infant cannot survive, to what appears to be excellent health.
- When a birth defect is genetic, it is not always inherited. A new change in the gene (a new mutation that produces an allele), or an abnormal dose of chromosomes from imbalanced contributions of egg or sperm, or errors in early division of the fertilized egg, may be the cause of the genetic abnormality, rather than the passage of an abnormal gene from the parents. However, once a genetic or chromosomal abnormality has occurred - it can ordinarily be passed on by the person who has it.
- Some birth defects occur because infections by bacteria or viruses that entered the baby's body during development. These include, as examples, Congenital CMV infection and Congenital Syphilis.
- When the placenta or womb fail to nourish the baby adequately, or anbormally constrict the developing baby's movements, birth defects can occur.
- Finally, the cause of a large number of birth defects is unknown. Despite meticulous work-up, the cause of some abnormalities is idiopathic, there is no evidence of any of the causes mentioned above.
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- Coakley LN. Preventable birth defects: a golden teaching opportunity. Journal of Christian Nursing. 24(3):126-32; quiz 133-4, 2007 Jul-Sep.
- Sokol, R. J., Delaney-Black, V., & Nordstrom, B. (2005). Fetal alcohol spectrum disorder. Journal of the American Medical Association, 290 (22), 2996
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