Blood chromosome testing

Chromosome abnormalites can impact on our genetic health in a variety of ways. In infants and children they may be the cause of newborn birth defects, developmental delay and/or mental retardation; see newborn birth defects and chromosome abnormalities. In adults they can affect fertility and reproductive health.

If a person has extra or missing whole chromosomes or parts of chromosomes, they will most likely have an unusual or abnormal appearance and/or intellectual handicap. For example, Down syndrome individuals have a characteristic appearance and have an extra chromosome 21, which is referred to as Trisomy 21. See Trisomy 21 karyotype.

Sometimes changes in chromosomes do not affect a persons appearance but will affect fertility, causing difficulty in falling pregnant or repeated miscarriage, or put them at risk for a chromosomally abnormal liveborn child. Structural chromosome rearrangements such as translocations are an example; see a translocation karyotype between Chromosomes 2 and 22. Other chromosome changes, such as sex chromosome anomalies, also can result in infertility.