CHROMOSOMAL ABNORMALITIES
Chromosomes are units of genetic information. Each individual have a complete set of chromosomes that is referred to as normal chromosomal complement. Abnormalities however may arise from a deficiency in either the total number of chromosomes or the structure. Chromosome abnormalities are caused at conception when an abnormal sperm or egg from the other parent. The abnormal sperm or egg contains extra or missing chromosome material. These abnormal sperm or eggs appear to be present in everyone, but the risk of an abnormal conception increases significantly with the parents ages. Majority of fetuses that suffer chromosomal end up as spontaneous abortions, while the minority that are delivered suffers from varing forms and severity of birth defects especially of the heart. The most common chromosome abnormality is down syndrome and is the commonest cause of severe mental retardation.
Prenatal diagnosis of chromosomal abnormalities involves the use of both screening and diagnostic techniques. The screening method that is widely used all over the world is a combination of maternal age, nuchal translucency scan and maternal serum biochemistry. This is the combination we also use in the centre to produce the most accurate risk value in all pregnant women. Diagnostic test involves invasive procedures such as aminocentesis or chorionic villous sampling to obtain a fetal sample for laboratory analysis. A chromosome test is performed on cells from the placental tissue (chorionic villi) to determine if the fetus has a chromosome abnormality. The test can also reveal the chromosomal sex of the fetus.
