Balanced reciprocal translocations: risk factors for aneuploid segregant viability

Abstract

Reciprocal translocations were studied in two groups of balanced carrier couples: 202 had 210 translocation aneuploid liveborn (LB) infants, and 95 couples had repetitive abortions (AB) without liveborn ancuploids. The observed translocation aneuploidies in the LB group were compared to predicted potential aneuploidies in A B by frequency of chromosome involvement, meiotic segregation mode, and mean trisomic, monosomic and combined genomic imbalances. Qualitative and quantitative differences identified genomic regions and chromosomes possibly vital for in utero survivability. LB aneuploidies indicate non‐random chromosome involvement, selection of least detrimental segregants and segments, and predominant transmission from maternal balanced carriers (especially in 3:1 tertiary segregation, 93.5%). For an individual with a balanced reciprocal translocation and untested reproductive capability, an approach is given for predicting whether a translocation aneuploid conceptus will be liveborn or aborted.

Reproductive outcome of couples with recurrent miscarriage and balanced chromosomal abnormalities

“…15,16,21 Only one study found an approximately equal number of female and male carriers among 95 couples with RPL. 22 We also observed an excess of female translocation carriers in our study. The proposed mechanism contributing to a higher incidence of female translocation carriers is that in female carriers only one ovum matures each month.…”

“…On the other hand, Davis et al . suggest a random involvement 22 . The total number of translocations observed in our series is only 48, too small to draw definitive conclusions.…”

“…Most researchers have reported that in couples with RPL, the number of female carriers of balanced chromosomal aberrations exceeded that of males significantly 15,16,21 . Only one study found an approximately equal number of female and male carriers among 95 couples with RPL 22 . We also observed an excess of female translocation carriers in our study.…”

Risk estimates for balanced reciprocal translocation carriers — prenatal diagnosis experience

“…The data presented here support the observation of Stengel-Rutkowski et al 1988, Stene 1989, and Midro et al 1992, that although there is a general tendency for reciprocal translocations ascertained through spontaneous abortions to represent a smaller risk than those ascertained through unbalanced offspring, this fact cannot be used in individual counselling as others have suggested (Daniel 1979, Davis et al 1985, BouC & Gallano 1986, Daniel et al, 1989. Namely, some reciprocal translocations carry a high risk of spontaneous abortions as well as a high risk of unbalanced progeny.…”

Alternate, adjacent 2 and 3:1 meiotic segregation products from a balanced t(13;18) (q12;q11) carrier

“…Acrocentric involvement is, however, present. Davis et al (1985) drew up tables aiming to predict segregation modes in balanced translocation carriers and then compared these with the observed results. The findings were largely predictive but adjacent 2 was not always consistent.…”