Testing for Chromosome Abnormalities After a Miscarriage

When Testing Is a Good Idea and What It Can Reveal

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The most common reason for a miscarriage is some sort of chromosome abnormality that causes the pregnancy to not be viable. That sounds scary, but in fact, for most couples who've gone through the pain of such a loss the odds are high they'll go on to conceive again and ultimately have a healthy baby. For this reason, doctors usually don't advise follow-up testing to try to find the cause of a first-time miscarriage, although some hopeful parents may feel that testing will help them find closure.

Chromosome testing is likely to be most useful after multiple miscarriages. In order to do it, a sample of tissue from the miscarriage must be collected and analyzed in a lab. The challenge, especially after a very early miscarriage, is it can be difficult to get an adequate sample unless a woman has had a dilation and curettage (D&C)—a procedure that involves removing any tissue that didn't pass during the miscarriage. If a woman begins bleeding in early pregnancy and feels certain she's having a miscarriage, her doctor or midwife can tell her how to save tissue to be analyzed. 

What Chromosome Testing Can Reveal

Based on the number of chromosomes and their structure, a chromosome test can confirm or rule out obvious abnormalities as the cause of a miscarriage. The most common chromosomal cause of miscarriage is trisomy. Others include triploidy, monosomy, tetraploidy, or structural malformations such as translocations—all of which usually are caused by sporadic abnormalities in the sperm or egg, rather than inherited from a parent.

Sometimes results showing normal chromosomes in a miscarried baby will be deemed conclusive only if the baby was a boy. Because well over half of chromosomally normal results from miscarriages tend to be female, researchers believe it's common for the mother's tissue to contaminate the results (although careful lab techniques may reduce the odds of this occurring). For cost and feasibility reasons, it's not possible to determine whether the test results came from the mother or from the baby in these cases.

Planning for Future Pregnancies

Regardless of the results, if you have a chromosome test after a miscarriage you'll likely have questions about how to plan for future pregnancies. A supportive doctor or genetic counselor should be able to answer your questions. And if your test results revealed a chromosomally normal pregnancy or were inconclusive, and you go on to have more miscarriages, you may wish to see a specialist who can test you for other miscarriage causes. 

If the results of your chromosome testing reveal that there was an abnormality, the odds are highest that it was a random one-time problem. It does not necessarily mean that you have an increased risk of having a baby with that abnormality in the future. Most chromosome abnormalities are the result of errors in cell division of the sperm or egg, and most of the time they will not recur in future pregnancies. The exception to this rule is if the results reveal that the baby had an unbalanced translocation, in which case the doctors may recommend you and your partner be tested for a condition called balanced translocation.

For couples who experience recurrent miscarriages and testing reveals this is happening because of chromosome abnormalities, there are ways to try to have a full-term pregnancy and healthy baby. One of these is a procedure known as pre-implantation genetic diagnosis, along with in-vitro fertilization (IVF). It's expensive and usually not covered by insurance, but certainly worth it for couples who deeply desire to have biological children of their own.

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