Mechanisms of CPM and UPD and Clinical Experience with CPM Found during CVS
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Dr. Laird Jackson, Drexel University, Department of Obstetrics & Gynecology, Philadelphia, Pennsylvania
CPM was first brought to attention by the work of Kalousek and Dill. Kalousek continued to push the field forward with many studies of placental cytogenetics. The general incidence of CPM from large collections of CVS data is between 1 percent and 2 percent of pregnancies studied by this technique. Inference from the occurrence of CPM in spontaneous abortus tissue suggests that the incidence per pregnancy is higher. CPM involves nearly every chromosome and the effects (if any) vary with the chromosome involved. Kalousek has categorized CPM into types depending upon the trophoblastic or fetal tissues (or both) involved. CPM can have a deleterious or a beneficial effect on pregnancy outcome depending upon its type. In addition, through the phenomenon of post-zygotic rescue of meiotic non-disjunction, UPD can be caused and exert its own effect on the fetus and its development. Collaborative collection of data under common protocol is likely necessary to develop data to further understanding and produce practical guidelines.