A birth defect is a structural, functional, or metabolic abnormality present at birth that results in physical or mental disability or death. There are more than 4,000 known birth defects, which may be caused by genetic or environmental factors. In the United States, about 150,000 babies are born each year with birth defects.
Some birth defects can be corrected by surgery after birth. Some examples are cleft palate, extra fingers or toes, webbed feet, club foot and 'hole in the heart'.
Birth defects may be caused by nutritional deficiencies of the mother and can be avoided by ensuring a good diet with supplemental vitamins and minerals and also by avoiding alcohol and tobacco. Folic acid is a common supplement.
There are potential birth defects that are genetic, and tests may be available to detect the condition in the womb or to test the parents and predict a potential risk if conception occurs. The parents can then assess the risk factors and decide to plan or avoid a pregnancy. They may also choose to conceive a child using in vitro fertilization and pre-implantation genetic diagnosis, or if the child is already conceived, end the pregnancy.
In the 1960s many birth defects were also caused by the usage of Thalidomide, a hypnotic drug administered to mothers to ease their pain during birth. The usage of this drug caused various defects, the majority of cases being deformities of the arms and legs.
Two of the tests for birth defects in fetuses are chorionic villus sampling (CVS) and amniocentesis. CVS tests cells from the placenta and amniocentesis tests cells from the amniotic fluid. However, it is not well understood what happens to abnormal cells.
A study published in 2016 found that in mice embryos where half the cells have an abnormal number of chromosomes, the abnormal cells are killed by apoptosis and the embryo continues to develop normally.
- "Early-stage embryos with abnormalities may still develop into healthy babies". 29 March 2016. University of Cambridge. Accessed 13 May 2018.
- McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.