Recurrence of Trisomic Pregnancies in Four Families: A Cytogenetic and Molecular Study
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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%.
KeywordsNondisjunction Trisomy 21 Trisomy 18 Recurrence Meiosis I Meiosis II
SN prepared the manuscript did detailed literature search. AVS did the molecular studies and wrote the interpretation. KMG reviewed the manuscript and had modified the interpretation of molecular results. LP and DY did detailed literature search and had helped in manuscript preparation. MVT and ZH had done the cytogenetic analysis for all four cases and have written the cytogenetic observations. KS has critically evaluated the manuscript and has contributed suggestions. SN had conceived the idea of drafting this paper and has done the final drafting and will act as the act as the guarantor of the manuscript.
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Conflict of interest
The authors declare that they have no conflict of interest.
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