Aneuploidy is most common genetic abnormality related to miscarriages. If the embryo does not have correct number of chromosomes then it has the wrong amount and type of DNA, it is called aneuploid. This can be compared to a cooking recipe: if you have the wrong ingredients or the wrong amounts of the ingredients, then the product will not come out right. Almost always the wrong number of chromosomes leads to miscarriage.
Aneuploidy accounts for the losses as a woman ages. Woman’s eggs are formed before she is born, then the eggs wait in the ovary until it their turn to be used (about 500-1000 eggs per month – only 1 ovulates). So as a woman ages, the eggs also age. The egg does not “mature” genetically until ovulation when it goes through the final steps of meiosis.
Meiosis is the term for the genetic process of reducing the amount of chromosomes in the cell by ½ so that when the sperm fertilizes the egg, the number of chromosomes is back to normal.
The spindle apparatus, which is a collection of micro-tubules helps line up the chromosomes and then the spindle apparatus pulls the chromosomes to the opposite ends of the cell so that the cell can divide and each “daughter cell” has the same number of chromosomes. Meiosis requires that the number of chromosomes divides in half so that when the sperm fertilizes the egg, the embryo will have a complete set of chromosomes.The frequency of aneuploidy in eggs increases as a woman ages.