Introduction: We report on the first successful preimplantation genetic diagnosis (PGD) in Singapore. Clinical Picture: A couple who are β-thalassaemia carriers and have an affected daughter requested for PGD. Treatment: Two cycles of PGD were performed on the couple. β-thalassaemia mutations were detected using a nested PCR and minisequencing strategy, and unaffected embryos were selected for transfer. Outcome: A singleton pregnancy was achieved in the second PGD cycle, resulting in the birth of a healthy baby boy with carrier genotype. Conclusions: This case report documents the first successful PGD in Singapore, involving a couple at-risk of transmitting β-thalassaemia major
As one of the most common genetic disorders worldwide, β-thalassaemia represents a significant healthcare burden in many countries in the malaria belt. In Singapore, the carrier frequency for β-thalassaemia mutations is 2.7% in the Chinese, 6.3% in the Malays and 0.7% in the Indians.1 Couples who are both heterozygous for the β-thalassaemia gene have a 25% risk of conceiving a child with β-thalassaemia major, a debilitating blood disorder requiring lifelong blood transfusions and associated with reduced life expectancy (~40 to 50 years). Genetic counselling and prenatal diagnosis enable at-risk couples to avoid having an affected child. Although these programmes have significantly decreased the number of births of β-thalassaemia major children in Singapore over the last 10 years,2 couples with an affected fetus are invariably faced with the difficult decision to terminate the pregnancy. Preimplantation genetic diagnosis (PGD) presents an alternative option to prenatal diagnosis. It involves in vitro fertilisation (IVF) followed by determination of the genetic status of embryos. As only the unaffected embryos are transferred to establish pregnancy, PGD may be an attractive option for at-risk couples who have had multiple affected pregnancies and resultant terminations, who have religious or cultural objections to pregnancy terminations, or who are secondarily sub-fertile and require assisted reproduction.
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