Prevention: prenatal diagnosis
Prevention of severe _- or _-thalassemia births by prenatal
diagnosis with termination of pregnancies has been available for
_ 2 decades, although it is among the most difficult ways to deal
with the disease.75 Acceptance of prenatatal diagnosis and termination
of affected fetuses are dependent on the early identification of
couples at risk, culturally sensitive genetic counseling, the cost, and
religious beliefs even when PCR technologies are available.
Preimplantation genetic diagnosis is also currently feasible, although
it is only available in some centers where conventional use
of in vitro fertilization is also available. In this case, DNA of a cell
from the blastomere is used for genetic diagnosis. However,
successful diagnosis may be compromised by failure to amplify
one of the 2 alleles in a heterozygous cell and/or by other
complications associated with in vitro fertilization.76
Current PCR technologies and precise hybridization assays to
detect single point mutations with great reliability using very small
DNA samples have been developed. Adequate amounts of fetal
DNA can be obtained safely around the 10th week of gestation by
chorionic villus sampling and up to the 18th week of gestation by
amniocentesis.1 New technology using fetal DNA obtained from
maternal plasma or maternal peripheral blood has also been
developed but is not routinely available.77,78
Prevention: prenatal diagnosisPrevention of severe _- or _-thalassemia births by prenataldiagnosis with termination of pregnancies has been available for_ 2 decades, although it is among the most difficult ways to dealwith the disease.75 Acceptance of prenatatal diagnosis and terminationof affected fetuses are dependent on the early identification ofcouples at risk, culturally sensitive genetic counseling, the cost, andreligious beliefs even when PCR technologies are available.Preimplantation genetic diagnosis is also currently feasible, althoughit is only available in some centers where conventional useof in vitro fertilization is also available. In this case, DNA of a cellfrom the blastomere is used for genetic diagnosis. However,successful diagnosis may be compromised by failure to amplifyone of the 2 alleles in a heterozygous cell and/or by othercomplications associated with in vitro fertilization.76Current PCR technologies and precise hybridization assays todetect single point mutations with great reliability using very smallDNA samples have been developed. Adequate amounts of fetalDNA can be obtained safely around the 10th week of gestation bychorionic villus sampling and up to the 18th week of gestation byamniocentesis.1 New technology using fetal DNA obtained frommaternal plasma or maternal peripheral blood has also beendeveloped but is not routinely available.77,78
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