Birth Defects Essay -- essays research papers fc

Birth defects, or congenital malformations, are the faulty formation of structures or body parts present at birth. Sporadic, hereditary, or acquired defects may be immediately observed or may become manifest later in life; they may be visible on the body surface or present internally. Birth defects may be life threatening and require surgical correction, or they may interfere with function or appearance. It is estimated that about 3% of all children are born with major defects; minor defects or variations are estimated to occur in 10% to 15% of births. Malformations may be single or multiple. Multiple malformations that occur in a regular recognizable pattern are referred to as syndromes--for example, the FETAL ALCOHOL SYNDROME sometimes observed in infants of mothers who drank heavily when pregnant. Birth defects may result from the action of genes, chromosomes, or the environment on the developing fetus, but often the cause cannot be determined. Inherited Defects Abnormal genes cause a significant number of different birth defects. Some can be identified as a single-gene disorder that is inherited in a simple Mendelian mode, that is, either a dominant or a recessive pattern. For example, lobster claw deformity of the hands and feet (split hands or feet) is inherited and results from the effect of a single dominant gene. A person who has this deformity runs a 50% risk (1 in 2) of bearing offspring who will inherit the gene and will therefore also be affected. Autosomal rece...