Few disorders can be more difficult to diagnose or more frustrating to treat then recurrent early pregnancy loss (REPL). Traditional diagnostic criteria call for at least three pregnancy losses prior to evaluation and treatment of this vexing problem. With more women choosing to delay pregnancy until their thirties or even their forties, REPL can create an additional burden on their already limited opportunities to achieve a successful pregnancy. Ironically, as women age they are more likely to experience a miscarriage when/if they do become pregnant. A new technique called comparative genomic hybridization (CGH) offers couples some reassurance.
Studies show that most pregnancy losses (50-70%) are due to genetic abnormalities. In fact, the earlier that miscarriage occurs the more likely it is to be due to abnormal changes in the DNA. These are not typically abnormalities that are detected by testing the parents but rather spontaneous mutations that occur during early development. Moreover, they often go undetected by the most commonly used technique for genetic assessment, called G-banded karyotype analysis. That’s because karyotype analysis has limited resolution. It is only able to detect the addition or deletion of relatively large portions of the genetic code. By contrast however, CGH is able to detect genetic changes that are far smaller. In fact, this technique has been reported to identify genetic causes for unexplained mental retardation in about 10% of patients that had previously had a “normal” conventional genetic karyotype. Moreover, a study in the current issue of the journal Obstetrics & Gynecology found that CGH was able to identify genetic abnormalities in 13% of miscarriages that were missed using conventional genetic testing. More exciting still is the potential of CGH to detect certain abnormalities before birth.
Maybe the best use of this technique however is when testing is performed on embryos prior to becoming pregnant. Combining CGH with in vitro fertilization (IVF) allows us to perform a biopsy upon an embryo for genetic analysis prior to transfer into a woman’s uterus. Early data using IVF with CGH has been very reassuring. We’re finding that by identifying and transferring only the embryos that are determined to be genetically competent—meaning without identifiable deletions or additions to the genetic code—we may be able to double or even triple the chance of a healthy live birth. Since this technique is still relatively new, more studies are needed before it is widely accepted but it is already revolutionizing the diagnosis and treatment of couples seeking fertility treatment.
Although we still recommend prenatal screening once pregnancy is established, CGH can dramatically reduce the anxiety of couples during those critical weeks of the first trimester; especially those with a history of recurrent early pregnancy loss. Remembering when my wife and I conceived—both of us are in our forties—I know that we would have had fewer sleepless nights early in our pregnancy had we been able to have CGH as part of our fertility treatment. There is certainly an additional therapeutic benefit of that stress reduction as well!