when are hereditary defects present in a developing fetus
Birth defect Genetic disorders or diseases are all congenital, though they may not be expressed or recognized until later in life. Genetic diseases may be divided into single-gene defects, multiple-gene disorders, or chromosomal defects. Single-gene defects may arise from abnormalities of both copies of an autosomal gene (a recessive disorder) or of only one of the two copies (a dominant disorder). Some conditions result from deletions or abnormalities of a few genes located contiguously on a chromosome. Chromosomal disorders involve the loss or duplication of larger portions of a chromosome (or an entire chromosome) containing hundreds of genes. Large chromosomal abnormalities always produce effects on many different body parts and organ systems.
Edwards syndrome Edwards syndrome, also known as trisomy 18, is a genetic disorder caused by the presence of all, or part of a third copy of chromosome 18.[2] Many parts of the body are affected.[2] Babies are often born small and have heart defects.[2] Other features include a small head, small jaw, clenched fists with overlapping fingers, and severe intellectual disability.[2]