Testing for Genetic Abnormalities

It is not unusual for multiple miscarriages to be a result of finding abnormal genetics in the fetus. When abnormalities are a recurrent problem, it may be due to unbalanced translocations. This is where parts of chromosomes break off and attach to each other, but there is not an equal exchange. Parents that carry balanced translocations are at higher risk for this. We recommend that all losses be tested for genetic abnormalities to eliminate this issue and allow us to focus on other possible causes. If the loss is diagnosed as female by genetic studies, it is important to also run a Maternal Contamination Screen to compare the mother’s genetics to the loss and ensure the results are not falsely reported as normal because the specimen was contaminated with the mother’s own tissue. The reports of a normal female without the MCS are of little value.

Through genetic testing, both parents can determine if they are carrying defects in their chromosomes (balanced translocations). Even when this is identified, couples ultimately conceive as long as additional thorough testing allows them to rule out other issues. Another difficulty in that patients have run into is pre-implantation genetic diagnosis (PGD). This is used as part of IVF and tests embryos prior to implantation.

The risk of PGD testing is that embryos which show abnormalities may be able to autocorrect themselves and proceed into a normal pregnancy. Some patients are told that most or all of their embryos were abnormal and will have few or none to transfer. Our belief is that the best approach is to effect as many transfers as possible then have successful implantations tested with CVS, a prenatal test for defects with much higher accuracy than PGD. Our research and experience have shown that there are often positive outcomes. It should be pointed out that patients who understand the loss of normal embryos but are still committed to only transferring normal embryos will still benefit from PGD or new methods of screening such as array CGH.

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