Genetics and one-off pregnancy loss

The genetic material that makes each of us unique is stored in structures called chromosomes.

Humans have 22 pairs of chromosomes - 1 set from each of their parents. The 23rd pair of chromosomes determine our sex- we get an X chromosome from our mothers. Boys get a Y chromosome from their fathers, and girls get an X chromosome from their mothers.

We have 46 chromosomes in total.

Every time a cell divides, there should be an exact copy of the chromosomes in each of the 2 new cells.

Scientists examine cells to determine whether or not they have the correct number of chromosomes in a procedure called a karyotype.

This is a normal karyotype:

Sometimes, however, the chromosomes do not replicate and divide properly, leading to chromosomal abnormalities. This is an example of a karyotype of a person who has 3 copies of chromosome 21, more commonly known as Down Syndrome:

In a small percentage of couples, between 3 and 5%, one partner possesses abnormal chromosomes that they repeatedly pass on to the fetus.

The most common condition is when the chromosomes, although being of the correct number, are arranged differently. This is called a balanced or reciprocal translocation and is a recognised cause of recurrent pregnancy loss.

If you would like to find out more about genetic testing, our Sydney Genetics website (www.sydneygenetics.com) website has lots of information.