Understanding Trisomy 22 Types and Their Link to Miscarriage

Chromosomal problems are a common cause of early pregnancy loss

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Chromosome problems, such as Trisomy 22, are by far the most common cause of first-trimester miscarriages. Depending on which chromosome is affected, extra or missing chromosomes (or parts of chromosomes) can cause anything from minor health problems to conditions incompatible with life. Trisomy 22 is one of the more severe chromosome disorders.

What Trisomy 22 Means

Trisomy 22 means that a person has three copies of the 22nd chromosome instead of the expected two copies.

The condition can be complete (meaning all cells in the body are affected) or mosaic (meaning some cells are affected but not others). It is also possible to have partial trisomy 22, meaning two complete copies of chromosome 22 and an additional incomplete copy of only part of the chromosome.

Diagnosis

Trisomy 22 can be diagnosed via genetic testing after a miscarriage or stillbirth. Prenatally it can be detected by CVS or amniocentesis, although prenatal test results showing trisomy 22 do not always mean that the baby will be significantly affected (see below).

Effects of Complete Trisomy 22

Complete trisomy 22 almost always causes first-trimester miscarriage; the condition is incompatible with life and there is no chance of a baby with complete trisomy 22 surviving in the long term. Researchers believe that trisomy 22 accounts for 3 to 5 percent of all early miscarriages.

Effects of Mosaic Trisomy 22

The effects of mosaic trisomy 22 may be mild in some individuals and serious in others.

Yet prenatal testing that finds mosaic trisomy 22 cannot predict the outcomes. Many babies who appear to have mosaic trisomy 22 in amniocentesis or CVS results do not have noticeable health problems at birth; babies confirmed as having mosaic trisomy 22 at birth are more likely to experience health problems.

If Your Baby Has Trisomy 22

If you have been told that a baby you miscarried had trisomy 22, rest assured that the miscarriage was not your fault and there was nothing you could have done to prevent it. Having one pregnancy affected by trisomy 22 does not mean that you have a higher risk of trisomy 22 in a future pregnancy. In most cases, trisomy 22 results from random problems in cell division and it doesn't recur.

If you are currently pregnant and have had a CVS showing trisomy 22, it's a good idea to talk to a genetic counselor or physician specializing in genetics. The chances are low that your baby has complete trisomy 22, and it is more likely that your baby either has mosaic trisomy 22 or a type of trisomy 22 that is present only in the placenta.

Your doctor may recommend an amniocentesis to shed further light on the situation. When the amniocentesis does not confirm the trisomy, the chances are high that the trisomy is only present in the placenta and the baby is chromosomally normal.

Yet there may be increased risk of intrauterine growth restriction and pregnancy complications due to the abnormal placenta, and you may need extra monitoring for the remainder of your pregnancy.

If the amniocentesis does confirm mosaicism in the baby, your genetic counselor or other genetics specialist can give you the most up-to-date information on what to expect.

Source

Trisomy 22 mosaicism. University of British Columbia. Accessed: Apr. 14, 2009. 

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