A birth defect is, in simple terms, a defect that is present at, or soon after, birth. There are many, many different kinds of defects, and many different causes of defects. They can also be relatively unimportant defects, such as a birthmark, or they can be major and life-threatening, such as a large hole in the heart. About 5% of babies are born with a birth defect, of which two thirds are considered to be minor.
Genetic – this is where the baby has a chromosomal abnormality, such as an extra chromosome 23 in Down's syndrome, or there is a defect on a chromosome that has either been passed down from the mother or father, or has randomly mutated. And example of this would be osteogensis imperfecta or cystic fibrosis.
Drugs – some drugs taken by the mother during pregnancy can cause birth defects; the obvious example of this would be the thalidomide deformities from the 1960s, where children were born with abnormally developed limbs. Smoking and alcohol can cause the baby to be born smaller than would normally be expected, and with potential problems, such as learning disabilities, that will only be discovered later on in the child’s life.
Radiation – if a pregnant woman is exposed to radiation sources, such as x-rays, it can cause genetic abnormalities in the growing foetus.
Infections – rubella is a notoriously damaging virus to babies in the womb, especially early on in the pregnancy. Pregnant women should also avoid cats during their pregnancy because of the risk of contracting toxoplasmosis, which can damage a developing baby’s organs.
Nutrition – if a woman’s diet is low in folic acid when she conceives, then there is a high risk of the baby developing spina bifida.
Other – some birth defects have an unknown causes, such as heart defects (hole in the heart, transposition of the great vessels.)
There are many different kinds of defect, but some of the common birth defects in the UK include:
Club foot – the baby’s foot is twisted out of shape and position
Hypospadiasis and epispadiasis – the urethral opening on the baby’s penis is out of place
Heart defects – there are many kinds of congenital heart defects, of varying severity
Polydactyly – extra fingers and toes
Cleft lips and cleft palates – where the bones and tissues of the roof of the mouth fail to develop correctly
Down's syndrome – and extra chromosome 23, which causes a large range of defects
Syndactyly – fingers or toes fused together
Spinal cord defects – such as spina bifida
Some birth defects cannot be predicted, but there are steps a woman can take to reduce the chances of a defect occuring. Simple measures include not smoking or drinking during the pregnancy, taking folic acid supplements before she gets pregnant, and having a rubella vaccination. It is best that she contact her doctor or midwife for further advice.
Genetic counselling may be offered to those with a family history or certain illnesses, such as already having one child with cystic fibrosis. The most obvious way of checking if a foetus has a birth defect is to perform an ultrasound scan. Other tests can be done on the foetus while it is in the womb to see if there is a genetic defect, using chorionic villus sampling, or amniocentesis; however, these tests do carry a risk of causing a miscarriage.