Risk estimates for balanced reciprocal translocation carriers — prenatal diagnosis experience

Abstract

An analysis was performed on 40 families at risk for an unbalanced rearrangement in the fetus because one of the parents is a reciprocal translocation carrier. The overall risk at second trimester prenatal diagnosis was 14% (8/57). The individual risks for unbalanced offspring at second trimester prenatal diagnoses and at birth were estimated using empirical data by Stengel‐Rutkowski et al. (1988). The risks at birth ranged from 0%–21.6%. Most reciprocal translocations (22 or 55%) were at low risk. Without risk (7 or 17.5%), medium risk (6 or 15%) and high risk (5 or 12.5%) translocations were about equally represented and relatively infrequent. The analysis shows that the mode of ascertainment as well as the measurement of lengths of observed or probable imbalances cannot serve as a reliable risk predictor in individual counselling. In the translocations ascertained through spontaneous abortions the risk is frequently small or nonexistent, but remarkable exceptions to this rule are observed. Translocations discovered through unbalanced offspring were found to belong to different risk groups with the exception of the no risk group. Individual risk estimates have to be performed as a basis of genetic counselling before or during pregnancy so that parents with reciprocal translocations can make their choices regarding the available options.

Risk evaluation of carriers with chromosome reciprocal translocation t(7;13)(q34;q13) and concomitant meiotic segregation analyzed by FISH on ejaculated spermatozoa

“…In the case of RCT carriers a genetic counseling should be offered and probability rates should be estimated for all particular types of pathology (unbalanced progeny at birth and at prenatal diagnosis, unkaryotyped miscarriages, stillbirth/early death newborns). This can be done on the basis of segregation analysis of pedigrees, if available [Stengel‐Rutkowski et al, 1988; Midro et al, 1992, 2000; Barisic et al, 1996; Stasiewicz‐Jarocka et al, 2004]. To assess the probability rate of the presence of unbalanced progeny, the information on given combinations of chromosome segments in the karyotype of the offspring of the individual RCT carrier, and the information about the number of normal offspring should be obtained directly from the analysis of a relative large pedigree consisted of several generations and many members.…”

Clinical outcomes for couples containing a reciprocal chromosome translocation carrier without preimplantation genetic diagnosis

“…Carriers of RCT tend to have a normal phenotype but have an increased risk of producing gametes with an unbalanced karyotype. These karyotypes are believed to be associated with infertility, recurrent spontaneous abortion, stillbirth, and birth of offspring with congenital anomalies . If RCT is diagnosed in one member of a couple, the couple is faced with three options to achieve pregnancy: natural pregnancy followed by prenatal diagnosis, pregnancy through assisted reproductive technology (ART) with preimplantation genetic diagnosis (PGD), or pregnancy through ART without PGD.…”