birth defects definition of birth defects in the Free Online Encyclopedia.

birth defects, abnormalities in physical or mental structure or function that are present at birth. They range from minor to seriously deforming or life-threatening. A major defect of some type occurs in approximately 3% of all births. Defects may be genetic in origin, as in Down syndrome Down syndrome, congenital disorder characterized by mild to severe mental retardation , slow physical development, and characteristic physical features. Down syndrome affects about 1 in every 730 live births and occurs in all populations equally.
..... Click the link for more information. , Tay-Sachs disease Tay-Sachs disease (tā`-săks`)
..... Click the link for more information. , sickle cell disease sickle cell disease or sickle cell anemia, inherited disorder of the blood in which the oxygen-carrying hemoglobin pigment in erythrocytes (red blood cells) is abnormal.
..... Click the link for more information. , and hemophilia hemophilia (hē'məfĭl`ēə,–fēl`yə)
..... Click the link for more information. , or may be the result of infections, such as rubella rubella or German measles, acute infectious disease of children and young adults. It is caused by a filterable virus that is spread by droplet spray from the respiratory tract of an infected individual.
..... Click the link for more information. and sexually transmitted diseases sexually transmitted disease (STD) or venereal disease, term for infections acquired mainly through sexual contact. Five diseases were traditionally known as venereal diseases: gonorrhea , syphilis , and the less common granuloma inguinale,
..... Click the link for more information. . Other teratogenic (malformation-causing) agents include drugs or hormones taken by the mother (e.g., thalidomide thalidomide (thəlĭd`əmĭd'), sleep-inducing drug found to produce skeletal defects in developing fetuses.
..... Click the link for more information. and DES DES or diethylstilbestrol (dī'ĕth'əlstĭlbĕs`trôl)
..... Click the link for more information. ) and maternal illnesses (e.g., diabetes diabetes or diabetes mellitus (məlī`təs)
..... Click the link for more information. ). The mother's nutrition, drinking (see fetal alcohol syndrome fetal alcohol syndrome (FAS), pattern of physical, developmental, and psychological abnormalities seen in babies born to mothers who consumed alcohol during pregnancy .
..... Click the link for more information. ), smoking smoking, inhalation and exhalation of the fumes of burning tobacco in cigars and cigarettes and pipes. Some persons draw the smoke into their lungs; others do not. Smoking was probably first practiced by the indigenous peoples of the Western Hemisphere.
..... Click the link for more information. , and drug abuse, as well as exposure to toxic chemicals and radiation, can also affect the developing fetus. Smoking, drugs, toxic chemicals, and the like can also damage the father's sperm, which may pass on the defect to the embryo in fertilization. The incidence of some disorders is elevated when the mother or father is older, which increases the likelihood of age-related gene mutations. Certain birth defects can now be detected prenatally through amniocentesis amniocentesis (ăm'nēō'sĕntē`sĭs)
..... Click the link for more information. and chorionic villus sampling chorionic villus sampling (CVS) or chorionic villus biopsy (CVB) (kōr'ē-ŏn`ĭk, kôr'–)
..... Click the link for more information. . Surgical procedures to correct certain disorders before birth are still considered experimental.