You and your husband have wanted to start a family ever since you met, but the journey to conceiving a baby hasn’t been as smooth sailing as you imagined. A couple of years ago, you endured your first miscarriage. After taking some time to recover emotionally and physically, you decided to try again. But three months in, another devastating blow occurred - a second miscarriage.

Now that you’re considering trying a third time, you’re wondering whether there’s something wrong. Why do you keep having recurring miscarriages? And is there something you can do to ensure a successful pregnancy?

Enduring recurrent miscarriages is one of the most devastating life events a person can go through. It’s common for the person who keeps having them to wonder if they will ever reach their end goal of producing a healthy baby. If you can relate to this, then we want you to know that we feel your pain, you are not alone, and that most of all, you and your body are NOT a failure.

Throughout the terrible frustration and pain of recurrent miscarriage, some parents find it helpful to have some understanding of the science behind the genetic causes of these events.

Here are two of the most common genetic causes behind recurrent miscarriage:

Recurrent aneuploidy

The first way in which a baby might end up with abnormal chromosomes and therefore result in being miscarried is recurrent aneuploidy. The term ‘aneuploidy’ is used as a description for any pregnancy without the correct number of 46 chromosomes.

An aneuploidy is an event that occurs ‘out of the blue’ before or after fertilisation of the egg called non-disjunction. Nondisjunction results in the incorrect number of chromosomes being present in the embryo. Examples of this include Down’s syndrome and Turner’s syndrome, where only one X chromosome is present.

While aneuploidies are usually associated with sporadic miscarriage, there are some couples who are at risk of repeated sporadic events. These are couples who produce chromosomally abnormal eggs or sperm. However, it’s important to note that the risk of having another miscarriage after miscarrying a chromosomally abnormal pregnancy is very low.

Chromosome abnormalities in the parents

In couples that have experienced recurrent miscarriages, an abnormality in one of the parents’ chromosomes might be the cause. This is a problem found in no more than 2 - 3% of couples with recurrent miscarriages.

One of the most frequent chromosomal abnormalities found in parents who experience this problem is a balanced translocation. This describes a situation that occurs when a fragment of one chromosome becomes attached to the broken end of another. Although it is not known what causes this, it has been linked to exposure to radiation. When the parent with the balanced translocation produces eggs or sperm, some will be normal but others will inherit the abnormality. It is down to luck whether the embryo they go on to make will consist of a normal egg or sperm, will become a balanced translocation carrier, or become unbalanced. If the embryo results in being unbalanced, the baby it will go on to become will rarely be born alive.

This information scratches the surface of how complex the genetic causes behind recurrent miscarriages are. While you can always delve deeper into your research, some parents find that getting too bogged down in the genetics can be counterproductive. If you want to know as much information as possible, talk to your doctor or specialist about how much information is necessary for you to know, and what will be helpful and positive for your fertility journey going forward.

What are the genetic causes behind recurrent miscarriage?

Unii looks at a heartbreaking question for any parent.