Abstract
Translocation carriers have an increased risk of miscarriage or the birth of a child with congenital anomalies. Preimplantation genetic diagnosis (PGD) is performed in translocation carriers to select for balanced embryos and, thus, increase the chance of an ongoing pregnancy. However, a common experience is that reciprocal translocation carriers produce a high percentage of unbalanced embryos, which cannot be transferred. Therefore, the pregnancy rates in PGD in this patient group are low. In a cohort of 85 reciprocal translocation carriers undergoing PGD we have searched for cytogenetic characteristics of the translocations that can predict the percentage of balanced embryos. Using shape algorithms, the most likely segregation mode per translocation was determined. Shape algorithm, breakpoint location, and relative chromosome segment sizes proved not to be independent predictors of the percentage of balanced embryos. The ratio of the relative sizes of the translocated segments of both translocation chromosomes can give some insight into the chance of transferable embryos: Very asymmetrical translocations have a higher risk of unbalanced products (p = 0.048). Counseling of the couples on the pros and cons of all their reproductive options remains very important.
Highlights
Since 1997 preimplantation genetic diagnosis (PGD) has been performed worldwide to allow translocation carriers to conceive balanced offspring and decrease the risk of miscarriages
Preimplantation genetic diagnosis (PGD) was performed in 85 couples with 83 different reciprocal translocations
We focused on the part of the PGD trajectory from oocyte retrieval to embryo transfer, as that is the success-limiting part in PGD for reciprocal translocations
Summary
Since 1997 preimplantation genetic diagnosis (PGD) has been performed worldwide to allow translocation carriers to conceive balanced offspring and decrease the risk of miscarriages. Other studies indicate that the live birth rate after PGD is not significantly different from spontaneous conception [8] This might be explained by the fact that in translocation carriers, especially reciprocal translocation carriers, 67% to over 80% of embryos are found to be chromosomally abnormal [1,9,10,11]. A clinical geneticist estimates the risk of viable unbalanced offspring based on the translocation at hand with its unique breakpoints and expected segregation modes, and the family history These estimates are based on spontaneous conceptions, without the use of assisted reproductive technology (ART) [14,15,16]. We hypothesized that differentiation of reciprocal translocations based on particular characteristics may be used in predicting the chance of transferable embryos in PGD cycles, and subsequent live birth rates
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