Question
What is Down syndrome, and what are its possible causes?
Answer
Down syndrome is primarily caused by chromosomal abnormalities, specifically an extra chromosome 21. This is usually due to incomplete cell division during the formation of the fertilized egg from sperm and egg. If a Down syndrome risk is detected during a mid-pregnancy screening, it may be due to the parents’ age, genetic factors, environmental factors (such as smoking, alcoholism, radiation, etc.), or sporadic genetic mutations. The occurrence of Down syndrome is not necessarily related to family history, as it may arise from new genetic mutations.