Prenatal diagnosis of Hb Bart's hydrops fetalis by PCR technique: Pramongkutklao experience.

Hb Bart's hydrops fetalis is very common in Southeast Asia, especially in Thailand. As the mother of such an infant may suffer from toxemia of pregnancy, ante- or post-partum hemorrhage as well as the psychological burden for carrying a nonviable fetus to term, so prenatal diagnosis is indicated and the family should be given the choice of early termination of the pregnancy. Seven high risk pregnancies with Hb Bart's hydrops fetalis (homozygous alpha-thalassemia 1) were studied. Amniocentesis was done at 16-33 weeks of gestation. DNA analysis was performed by polymerase chain reaction (PCR) using 2 techniques, 1) three nucleotide primers and 2) four nucleotide primers. After either therapeutic abortion or birth, heart blood or cord blood was drawn to confirm the diagnosis by Hb electrophoresis and DNA analysis. Of 7 high risk fetuses, 3 were recognized as Hb Bart's hydrops fetalis, 2 showed the alpha-thal 1 trait, 1 showed alpha-thal 2 trait and 1 was a normal fetus. The technique was entirely suitable for prenatal diagnosis of Hb Bart's hydrops fetalis. This technique was a rapid, simple non-radioactive method, less expensive and available in most PCR laboratories.