Can Characteristics of Reciprocal Translocations Predict the Chance of Transferable Embryos in PGD Cycles?

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.

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

“…This finding is consistent with results obtained from the European Society of Human Reproduction and Embryology PGD Consortium and from other authors . However, other researchers have reported that abnormal gamete rate could differ by the sex of the RCT carrier; the abnormal embryos are totally different, which might cause the different clinical outcomes.…”

Detection of a balanced translocation carrier through trophectoderm biopsy analysis: a case report

“…Due to the diagnosis of a balanced translocation in the mother, the only euploid embryo from the first IVF cycle was re-classified as either 46,XX or 46,XX,t(7;10)(q21.11;q11.23) and transferred, but without resulting in pregnancy. Because most reciprocal translocations have various segregation modes, depending on chromosomes involved, localization of breakpoints and translocated segment sizes and carrier gender [14, 15], empirical data on the risks for viable unbalanced offspring can be lacking, and for each individual couple risk estimation is based on the detected balanced translocation and family history. In the current case, no further counselling was requested by the couple after the diagnosis of a balanced translocation in the mother, and the female patient continued with IVF treatment and embryo testing.…”