Causes of Edwards’ Syndrome
The causes of Edwards’ syndrome lie in a genetic abnormality known as trisomy 18. In this condition, a baby has three copies of chromosome 18 instead of the usual two. This extra chromosome affects nearly every organ and system in the developing body, leading to a wide range of health problems. Edwards’ syndrome is not usually inherited—it occurs as a random event during the formation of reproductive cells.
During fertilisation, an egg from the mother and a sperm from the father combine to form a new life with 46 chromosomes—23 from each parent. In trisomy 18, one of the parents’ cells contributes an extra chromosome 18. This typically happens due to a process called nondisjunction, where chromosomes fail to separate properly during cell division.
There are three types of Edwards’ syndrome:
Full trisomy 18 – where every cell in the body contains an extra chromosome 18. This is the most common and most severe form.
Mosaic trisomy 18 – where only some cells have the extra chromosome. The symptoms may be milder depending on the number and type of affected cells.
Partial trisomy 18 – where only a part of chromosome 18 is present in triplicate. This is rare and often caused by a piece of the chromosome attaching to another during cell formation.
The exact reason for these chromosomal errors is not well understood, but they are more likely to happen as a woman gets older. The risk increases significantly for mothers aged 35 and above.
Causes of Edwards’ Syndrome
In South Africa, many women may not be aware of these risks, especially in areas with limited access to antenatal education. Routine prenatal screenings may not always be offered, particularly in underfunded clinics. Increasing awareness of maternal age-related risks and improving access to prenatal diagnostics could help identify Edwards’ syndrome earlier.
Although the condition usually occurs by chance, parents who have had one child with Edwards’ syndrome may be offered genetic counselling. This can help them understand their risk in future pregnancies and explore available options.
Understanding the causes of Edwards’ syndrome allows for better screening and emotional preparation. It also supports more informed conversations between parents and healthcare providers when faced with difficult decisions.
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