CONFINED PLACENTAL MOSAICISM AND STILLBIRTH

The cause of stillbirth can usually be determined in only 20% of cases . An increased frequency of adverse pregnancy outcome, including pregn ancy loss, intrauterine growth restriction, and premature labor, has b een observed in association with confined placental mosaicism (CPM), w hich is characterized by a discrepancy between the karyotype of the fe tus and placenta. Specific chromosomal trisomies have been observed in CPM more frequently than others, with trisomy of chromosomes 7, 16, a nd 18 being the most prevalent. In pregnancies with CPM it has been sh own that the zygote is often trisomic, and postzygotic loss of the add itional chromosome occurred in the embryonic progenitor cells leading to a dichotomy between the placenta and the embryo/fetus. In one third of such cases fetal uniparental disomy (UPD), which is the presence o f both homologues of a chromosome derived from one parent, can be expe cted. The specific role of the trisomic placenta and the presence of f etal UPD in cases of altered intrauterine fetal development has not be en fully established for various chromosomes. Therefore, to enhance ou r understanding of the pathogenesis of stillbirth it is imperative tha t cytogenetic analysis of both fetal and placental tissues be performe d in all cases of unexplained stillbirth.