Parental Karyotype Tests for Recurrent Miscarriages

Parental Karyotype Tests Assess Miscarriage Risk

Pregnant couple talking with doctor in waiting room
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About 4 percent of couples with recurrent miscarriages have chromosome abnormalities in one or both parents that can recur in future pregnancies, so some physicians suggest parental karyotype tests as a part of investigating the cause.

Chromosome problems cause more than half of all miscarriages. In most cases, the problems arise during the formation of the sperm or egg and are not inherited from the parents, so the odds are your next pregnancy won't have the same outcome.

 

What Are Karyotype Tests?

A karyotype test is not a comprehensive test for every known genetic disorder. Instead, the test evaluates the number and structure of the chromosomes.

Human cells are supposed to have 46 chromosomes (23 pairs), so a karyotype test can detect deviations from that number as well as abnormalities in chromosome formation.

From a miscarriage perspective, a physician recommends karyotype tests for prospective parents to detect underlying issues or on tissue from the pregnancy to detect issues present in a specific baby.

Parental Karyotypes and Miscarriage Risk

Underlying chromosome issues affect only a very small number of couples having recurrent miscarriages. The most common condition in these couples is balanced translocation, meaning parts of the chromosomes are rearranged.

A karyotype may also reveal other types of translocations or a condition called chromosomal mosaicism.

Who Should Have Parental KaryotypeTests?

Some, but not all, physicians include parental karyotyping as a routine test for couples who have had multiple miscarriages. Other physicians use the test only for couples with a higher risk of having a chromosome-related condition. It's common to test both parents.

A big reason why many doctors do not order parental karyotypes routinely is that even if the test finds an abnormality, there really isn't anything you can do about it because most couples with abnormal karyotypes just keep trying.

Does IVF Reduce the Risk of Miscarriage?

The one possible treatment in these cases is to attempt in vitro fertilization (IVF) with pre-implantation genetic testing of the embryos. But using intervention does not appear to change the ultimate outcomes.

IVF may speed up the process of having a normal pregnancy, and some doctors do support using it, but IVF is also prohibitive for many couples because it's:

  • invasive
  • expensive
  • frequently not covered by health insurance

Actually, research shows that compared to couples who use IVF, couples who keep trying with no intervention have about the same odds (around 68 percent) of eventually having a normal pregnancy.

The Value of Parental Karyotype Testing

Given that physicians typically advise couples with a proven chromosome issue to continue trying to conceive normally, the value of parental chromosome testing is debatable.

Still many doctors and prospective parents prefer to have as much information as possible.

If you do have the test and receive abnormal results, a genetic counselor can probably help you figure out where to go from here. On the other hand, if the results are normal, you will know that there is no known chromosome disorder affecting your odds of a successful pregnancy.

Sources:

Stephenson, Mary D. and Sony Sierra. "Reproductive outcomes in recurrent pregnancy loss associated with a parental carrier of a structural chromosome rearrangement." Human Reproduction 2006 21(4):1076-1082.

Sugiura-Ogasawara, Mayumi and Kaoru Suzumori. "Can preimplantation genetic diagnosis improve success rates in recurrent aborters with translocations?" Human Reproduction 2005 20(12):3267-3270.

Using Karyotypes to Predict Genetic Disorders. University of Utah Genetic Science Learning Center. Accessed: May 16, 2009.

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