Risk of mosaicism and uniparental disomy associated with the prenatal diagnosis of a non-homologous Robertsonian translocation carrier.
OBJECTIVE
To estimate the fetal risk of uniparental disomy (UPD) associated with the presence of a Robertsonian translocation (RT) in a parent or in the fetus, to determine whether it is clinically indicated to test these pregnancies for UPD.


METHODS
Retrospective analysis of our Centre's experience in testing prenatal specimens for UPD in cases of known familial RTs or fortuitous RT finding. In addition, all reports dealing with prenatal UPD testing in similar populations obtained from PUBMED and the 1995-2001 American Society of Human Genetics Meeting's abstracts were assessed.


RESULTS
No case of UPD 14 or 15 was found among the 51 tests performed at our Centre. Meta-analysis identified one case of UPD13 out of 687 UPD studies, conducted in 400 prenatal diagnoses. The 95% confidence interval of the risk of UPD in the population studied (1 in 738) is 0.02-0.76%. In one report, trisomy mosaicism for one of the chromosomes involved in the translocation was found in 3 cases out of 169 (95% confidence interval: 0.1-3 %).


CONCLUSIONS
Fetuses carrying a Robertsonian translocation have a risk of UPD of 0.02-0.76% (95% CI). In this population, trisomy mosaicism is more frequent than UPD. This finding justifies the study of additional colonies in all cases of prenatally diagnosed RT.
Department of Pathology, University of British Columbia, Vancouver, B.C., Canada. hbruyere@vanhosp.bc.ca
H
H
Bruyère
R D
RD
Wilson
S
S
Langlois
D002883:Chromosomes, Human, Pair 14 / Q000235:genetics; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics; D005260:Female; D006579:Heterozygote; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009030:Mosaicism; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012189:Retrospective Studies; D012307:Risk Factors; D014178:Translocation, Genetic; D024182:Uniparental Disomy / Q000175:diagnosis / Q000209:etiology* / Q000235:genetics