Virtus Genetics
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Miscarriage causes & recurrent miscarriage

Sadly, we know that miscarriage occurs in one in four pregnancies. This is little consolation when you have lost a baby through miscarriage, and you may want to find out why it occurred and if you can reduce the risk of it happening again.

The vast majority of patients who have experienced a miscarriage will go on to achieve a healthy family, so it’s important to stay positive. However, a small percentage of couples will experience more than one consecutive miscarriage. If you have three or more consecutive early pregnancy losses this is called recurrent miscarriage, and affects about 2% of women trying to have a baby.

What causes a miscarriage?

Some of the causes of miscarriage include:

- Random chromosome variations
- Genetic variations
- Parental chromosome variations
- Uterine variations
- Immune causes
- Blood clotting disorders
- Other medical conditions
- Hormone imbalances

Chromosomal variations - genetic problems with the embryo

One of the most common reasons why IVF is unsuccessful, or why miscarriages occur, is because of chromosomal variations in the embryo.

Up to 70% of embryos, whether created naturally or through IVF, are lost before birth. This usually occurs within the first three months of pregnancy, most often before implantation.

What is a chromosome? 

A human cell contains genetic material arranged in dense strands, called chromosomes. A normal cell will contain 23 pairs of chromosomes. Fertilisation combines 22 chromosomes and an X chromosome from the mother’s egg with 22 chromosomes and either an X or Y chromosome from the father’s sperm. An embryo then has 46 chromosomes – if it’s a female, with two X chromosomes, and if it’s a male, with an X and a Y chromosome.

If the cells of an embryo contain the wrong number of chromosomes this is called aneuploidy, and causes the embryo to develop abnormally. Women over 38 years of age are at greatest risk of conceiving a baby with a chromosomal variations.

Sometimes pieces of chromosomes break off and attach to the ends of other chromosomes. You would then have a normal number of chromosomes (known as balanced translocation), but your children may inherit the chromosome with one part missing, or the chromosome with an extra part (unbalanced translocation). Embryos with unbalanced translocations will usually miscarry or fail to implant.

Testing for genetic diseases

A gene is a sequence of DNA (genetic material) on a chromosome with a particular function. Humans have up to 20,000 different genes. When the DNA sequence on a particular gene is altered, a genetic variation such as cystic fibrosis or thalassaemia may result. It is now possible to test embryos for many single gene disorders or chromosomal variations with Pre-implantation Genetic Testing (PGT).

Some of the most common conditions tested for include:

• Huntington's disease (direct and exclusion)
• Cystic Fibrosis
• Thalassaemia
• Duchenne muscular dystrophy
• Fragile–X
• BRCA1/BRCA2 (hereditary breast / ovarian cancer)

Advanced embryo selection

As part of the Virtus Health Group of IVF Clinics, have been involved in a scientific breakthrough with the world’s fastest and most precise embryo selection test.

By screening all chromosomes in a developing embryo we can select the embryo with the greatest chance of success. This can address some of the key causes of miscarriage, and give some certainty to couples who have experienced recurrent miscarriage.