Genetic Causes of Recurrent Miscarriage

When couples face repeated miscarriages, they often ask if something is wrong in their genes. The honest answer is that genetics plays a major role in miscarriage, but in most cases it is a chance event, not something inherited from the parents.

How do chromosomes cause miscarriage?

Humans have 46 chromosomes in 23 pairs, half from each parent. If an egg or sperm carries an extra or missing chromosome, the embryo usually cannot develop, and the pregnancy ends. This type of error becomes more common as a woman ages, and is the main reason miscarriage risk rises after 35.

Two types of genetic causes

1. Chance errors in the embryo (most common)

These happen at conception and are not inherited. They usually do not repeat, which is why most women who have had a miscarriage go on to have a healthy pregnancy.

2. Parental chromosomal rearrangement

One partner has a balanced translocation, where parts of two chromosomes have swapped places. The parent is healthy because no genetic material is lost, but their eggs or sperm may carry too much or too little, leading to miscarriage or a child with an abnormality. Inversions and other rearrangements are rarer.

How Common Is It?

A balanced translocation is found in about 2 to 4 percent of couples with recurrent miscarriage. It is more likely in couples with three or more losses, or with a family history of miscarriage, stillbirth or children with birth defects.

Which tests help?

Parental karyotype

A blood test that looks at the chromosomes of both partners. It is not routinely advised for all couples, but may be considered after repeated losses, particularly if tissue testing shows an unbalanced rearrangement.

Testing the miscarried tissue

Chromosome analysis (karyotype or microarray) of the products of conception shows whether the embryo had an error. If it did, the loss was probably due to chance, which can be reassuring.

Other genetic tests

• Carrier screening for specific conditions in selected couples
• Whole-exome tests in special situations

What happens if a rearrangement is found?

You will meet a genetic counsellor to discuss:

• The chance of an unaffected baby naturally
• Pre-implantation genetic testing for structural rearrangements (PGT-SR) with IVF, which tests embryos before transfer
• Prenatal diagnosis during natural pregnancy using CVS or amniocentesis
• Donor gametes in some cases
• Adoption and other family-building options

Many couples with a balanced translocation still have healthy children, with or without IVF.

Does genetic testing of embryos prevent miscarriage?

For couples with a known parental rearrangement, PGT-SR can reduce the chance of miscarriage. For unexplained recurrent miscarriage without a known rearrangement, routine PGT for aneuploidy has not been shown to increase live birth rates in all studies, and is still debated. Discuss with a specialist.

Do genes cause all miscarriages?

No. Other causes include uterine shape, antiphospholipid syndrome, thyroid disease, diabetes, infections and lifestyle factors. Many cases remain unexplained.

What can you do now?

• Keep a record of each loss, with dates and reports.
• Ask whether tissue testing is possible after a loss.
• Consult a fetal medicine or fertility specialist after two losses.
• Maintain a healthy lifestyle, treat thyroid and sugar issues, avoid smoking and alcohol.
• Consider counselling for emotional support.

When should you see a doctor?

Seek advice if you have had two or more miscarriages, a loss after a heartbeat was seen, a stillbirth, a child with a birth defect or a family history of genetic disease.

The takeaway

Finding a genetic reason can bring clarity and a plan. And when the cause is chance, it brings hope. For counselling and testing, consult Dr Malathi G. Prasad, a fetal medicine specialist at Trichy Fetal Medicine and Fertility Centre in Trichy.

For appointments, the genetic counselling page has the details, and our fetal medicine specialists can advise whether it fits your situation.

Related guides

• Before Trying to Conceive After a Miscarriage
• How Many Miscarriages Count as Recurrent Pregnancy Loss?
• What Tests Are Done After Repeated Miscarriages?
• Pregnancy After Recurrent Miscarriage: How It Is Monitored