Every human cell in our body has 23 pairs of chromosomes, totaling 46 chromosomes. Each chromosome contains hundreds to thousands of genes. Genetic & chromosomal abnormalities occur when there is an abnormality within a single gene, one chromosome, or an abnormal number of chromosomes.
These abnormalities can result from genetics/hereditary factors, genetic mutations, environmental factors, and exposure to certain substances in utero such as substance/drug use. Chromosomal abnormalities can result in developmental/cognitive delays and birth defects. Down syndrome (Trisomy 21) is a common type of chromosomal abnormality where there is an extra chromosome. Chromosomal abnormalities occur in utero, however are not all are evident at birth. Medical testing is required to determine the type of chromosomal abnormality/mutation.