Nonhomologous Robertsonian translocations (NHRTs) and uniparental disomy (UPD) risk: an Italian multicentric prenatal survey.

Objectives: The risk of uniparental disomy (UPD) occurrence associated with the prenatal finding of balanced nonhomologous Robertsonian translocations (NHRTs) has been estimated only on limited empirical data. The aim of the study was to verify the estimate of the general risk, to get narrower confidence intervals by cumulating the data and to obtain risk estimates for specific translocation types.
Methods: We tested for UPD 160 prenatal specimens referred to the participant centers after the cytogenetic finding of NHRT.
Results: One case of upd(14)mat was found, associated with a 45,XX,der(14;22)mat fetal karyotype. The general empirical risk of UPD occurrence in NHRT carrier fetuses, corrected for the actual number of chromosomes analyzed, was 0.76% (95% CI 0.02-4.25%). Cumulative data with previous studies gives a general risk of UPD associated with NHRT of 0.80% (95% CI 0.17-2.34%). The UPD risk for the specific NHRT der(13;14) did not significantly differ from that of the other NHRTs taken together.
Conclusion: The present survey confirms the previously estimated risk of occurrence of UPD in offspring of NHRT carriers as a low, but not negligible risk, worth being investigated in prenatal diagnosis.
(Copyright 2004 John Wiley & Sons, Ltd.)