Prenatal Diagnosis of � - Thalassemia

AbstractPrenatal diagnosis of β-thalassemia was attempted in 24 pregnancies. Adequate amounts of fetal blood were obtained in 23 cases by placental puncture between 18 and 23 weeks of gestation. The percentage of fetal blood obtained in the successful cases varied from 6.75 to 99.9%, and the volume ranged from 1 to 600 µl. Sampling was more successful in eight cases with posterior placenta, where the concentration of fetal blood ranged from 40.2 to 99.9%. Samples were incubated with [3H]leucine. After incubation, the samples with a fetal blood concentration < 80% (eight cases) were concentrated by differential agglutination with anti-i serum and with anti-AB serum (two cases with maternal blood group O and paternal group AB). The final concentration of fetal red blood cells after purification ranged frgm 49 to 98%. Three fetal losses occurred. In two cases, abortion was induced two days and one month, respectively, after the procedure as the fetuses were dead. In the third case, premature labor occurred at 28 weeks’ gestation; the 1-kg infant died after two days. Four fetuses with β:γ ratios of 0 and one with a ratio of 0.005 were considered homozygous. The diagnoses were confirmed after abortion. Twelve fetuses with β:γ ratios ranging from 0.038 to 0.064 were considered heterozygous and six fetuses with β:γ ratios ranging from 0.1 to 0.12 were considered normal. In five fetuses with β:γ ratios from 0.038 to 0.064, cord blood analysis demonstrated heterozygous infants at birth.