• Dr Peter Chew

What is aneuploidy? Why should age have anything to do with bad gene?

I am 38 and have been married for 3 years. I had 2 miscarriages over the past 2 years. My doctor told me that it was due to my age and my baby’s bad “genes” called “aneuploidy”. I don’t quite understand. What is aneuploidy? Why should age have anything to do with bad gene?


Aneuploidy refers to abnormal number of chromosomes in a cell. Chromosomes are organised structures in the nuclei of the cell. They contain DNA or genetic materials. Normal cells have 46 chromosomes comprising 23 chromosome pairs-- half from the mother and half from the father. Normally, the egg and sperm have 23 chromosomes each. When the egg is fertilized, the foetus has a total of 46 chromosomes. With advancing age, random error of cell division becomes more common. This results in a cell with either an extra or missing chromosome. The foetus may have cells with three copies of a particular chromosome (resulting in 47 total chromosomes) or one copy of a particular chromosome (resulting in 45 chromosomes). An extra copy of a chromosome is called a trisomy; a missing copy is called a monosomy. Changes in the number of chromosomes in the foetus or aneuploidy can affect the outcome of a pregnancy. Some aneuploidies can result in a live birth, but majority are lethal and result in miscarriages in the first trimester. It is estimated that more than 20 percent of pregnancies may have an aneuploidy, which usually does not recur in future pregnancies.




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