Where a gene has been altered or suddenly changed in some way, the resulting gene abnormality may be passed on to the child. These abnormalities are known as mutations, and are, fortunately, rare. Some mutations may be caused by exposure to radiation. X-rays or chemicals, but many are spontaneous, and once the change has taken place there is no cure (although some of the diseases caused can be cured). If a man or woman has a condition caused by a mutation, such as congenital dwarfism (stunted growth), it may be passed on through the sperm or the egg cells to any children.
Some congenital disorders may be caused by environmental factors, or environmental and hereditary factors linked together. Environmental factors are circumstances outside the body that affect the physical and mental development of the fetus and the child.
Examples of these factors are:
- Geographical location. (For example, Scotland has a higher percentage of heart disease than the rest of the United Kingdom.)
- Social environment. Poor health care, inferior housing and diet can produce a higher risk of congenital disorders.
- Education. Poor general or health education can result in people being unaware of what causes congenital handicap, and of the advice and treatment available.
- We can provide a good or a bad environment for children. A good environment will include sound antenatal and postnatal care, healthy living conditions, clean air and water, and opportunities for intellectual and emotional development. A poor environment can produce stunted physical growth, retardation in learning and intellectual development, and emotional problems.
Disease or deficiency while in the womb
Some congenital diseases can be contracted during the nine months of pregnancy by the infection being passed from the mother to the fetus. A typical example is rubella (German measles), which, if it does not result in a miscarriage for the mother, may cause deafness, cataracts or deformity in the child. Other virus infections can also be dangerous. Diseases as different as syphilis (an STD, now rare) and diabetes in the pregnant woman can cause severe problems for the unborn child. A poor or inadequate diet during pregnancy can make the fetus suffer a shortage of vitamins and minerals, resulting in a deficiency disease, and some drugs during pregnancy can have harmful effects. One of the most tragic cases occurred when pregnant women in the early 1960s were prescribed Thalidomide (a sedative), and a number of their babies were born with extremely serious limb deformities; but some antibiotics, steroids and hormones can be harmful to the unborn child too. Pregnant women should take only medicines that have been carefully selected to avoid harming the fetus.