PRENATAL-DIAGNOSIS OF A FETUS WITH 2 BALANCED DE-NOVO CHROMOSOME REARRANGEMENTS

Two apparently balanced chromosome rearrangements were identified in a 17-week fetus by analysis of cultured amniocytes, The fetal karyotype was 46,MZ,t(2;16) (q33; q24), inv(7)(p15q11.23). Parental karyotypes were normal, indicating a de novo origin of both chromosome rearrangem ents in the fetus, The risk of phenotypic abnormality from a de novo r eciprocal translocation or inversion has been estimated at approximate ly 7% [Warburton, 1991]. The risk of abnormality in this fetus was est imated to be a minimum of 14%, based on the additive risk of each rear rangement, equivalent to 3.5% per chromosome breakpoint. The pregnancy was terminated because of the risk of abnormality and the detection o f intrauterine growth retardation by ultrasound. In the absence of add itional experience, the minimum presumed risk of phenotypic abnormalit y for de novo, multiple or complex chromosome rearrangements identifie d prenatally may be estimated as the additive risk of the number of ch romosome breakpoints involved. (C) 1996 Wiley-Liss, Inc.