Recurrence of Trisomic Pregnancies in Four Families: A Cytogenetic and Molecular Study
Tóm tắt
The risk for recurrence of non disjunction trisomy 21 is conventionally considered to be less than 1%. Within a span of 3 years, we observed recurrence of non disjunction trisomies in four families. The objective of the present study was to determine low level mosaicism in either of the couple and to identify the parental origin of additional chromosome 21/18. The four couples who had recurrent trisomic conceptions were investigated for the underlying mosaicism by analysis of 100 cells from peripheral blood of the couple and the parental origin of supernumerary chromosome 21/18 were identified using microsatellite markers. Low level mosaicisms in peripheral lymphocytes of couple were ruled out for all four families. Microsatellite markers have shown maternal origin of chromosomal nondisjunction for all the families and defective first meiotic division as the most common mechanism for nondisjunction. This observation raises the need for discussing the option of invasive testing while counseling the couple with an affected child with non-disjunction trisomy as the risk for recurrence of trisomies in subsequent pregnancy might not be as low as 1%.
Tài liệu tham khảo
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