Preimplantation genetic diagnosis of chromosome translocations by analysis of polymorphic short tandem repeats

<p><b>INTRODUCTION</b>We aimed to develop and implement a short tandem repeat (STR) polymerase chain reaction alternative to fluorescence in situ hybridisation (FISH) for the preimplantation genetic diagnosis (PGD) of chromosomal translocations.</p><p><b>METHODS</b>Selected informative STRs located on translocated arms of relevant chromosomes were used to discriminate between normal and unbalanced chromosome states in each embryo.</p><p><b>RESULTS</b>PGD cycles were performed on five couples where one spouse carried a balanced translocation. 27 embryos were analysed, of which 12 were normal/balanced, 12 were abnormal/unbalanced and three were indeterminate. Four PGD cycles proceeded to embryo transfer, of which two led to pregnancy. The first pregnancy showed a normal male karyotype, and a healthy baby was delivered at term. A second pregnancy unexpectedly miscarried in the second trimester from unknown causes.</p><p><b>CONCLUSION</b>STR analysis is a simple and suitable alternative to FISH for detecting unbalanced chromosomal states in preimplantation embryos.</p>

Successful preimplantation genetic diagnosis of Hb Bart's hydrops fetalis in Singapore after fresh and frozen embryo replacement cycles

<p><b>INTRODUCTION</b>We report the fi rst successful preimplantation genetic diagnosis (PGD) for Hb Bart's hydrops fetalis in Singapore, involving both fresh and frozen embryo replacement cycles.</p><p><b>CLINICAL PICTURE</b>Two couples who were carriers of the Southeast Asian type double gene deletion (--(SEA) deletion carriers) requested for PGD. Couple A had 2 previous affected pregnancies, while couple B have a child of unknown genotypic status.</p><p><b>TREATMENT</b>One PGD cycle was performed for each couple. The --(SEA) deletion was detected using a gap-PCR strategy. Couple A had 1 fresh-embryo replacement cycle while couple B underwent 2 frozen-embryo replacement cycles.</p><p><b>OUTCOME</b>Couple A achieved a twin pregnancy. Second trimester complications resulted in premature delivery, where 1 baby girl survived. Couple B achieved a singleton pregnancy resulting in delivery of a healthy baby boy. Genotype analysis of all babies confirmed the PGD results consistent with clinically unaffected status.</p><p><b>CONCLUSIONS</b>We have successfully performed PGD to avoid Hb Bart's hydrops fetalis syndrome.</p>