Prenatal diagnosis of homozygous alpha-thalassemia-1 by cell-free fetal DNA in maternal plasma


  • Funding sources: This project was supported by the Thailand Research Fund (grant number RSA 5180013)
  • Conflicts of interest: None declared

Supatra Sirichotiyakul. E-mail:



To investigate the use of cell-free fetal DNA (cff-DNA) to determine fetal status in pregnant women who were risk for having Hb Bart's.


Plasma DNA was extracted from 10 mL of maternal blood from couples who both were alpha-thalassemia-1 carriers (SEA deletion). Real time quantitative PCR was performed using fluorescence-labeled probes to monitor wild type (wt) and SEA allele. The quantity of each allele was determined by cycle threshold (Ct). ΔCt (Ct of wt– Ct of SEA) was calculated from each sample. Prenatal diagnosis was performed to determine fetal status.


There were 62 Hb Bart's, 62 alpha-trait and 34 normal fetuses in this study. Mean ΔCt was 1.04 ± 0.38, 0.21 ± 0.37 and 0.14 ± 0.55 in Hb Bart's, alpha-trait and normal fetuses, respectively. Based on ROC, the best cut-off of ΔCt for predicting Hb Bart's was 0.51, giving 98.4% sensitivity and 20.8% false-positive rate. All but one Hb Bart's (98.4%) had ΔCt above 0.51, whereas 74.2% of alpha-trait and 88.2% of normal fetuses had ΔCt below 0.51.


There is a positive trend to use cff-DNA in maternal plasma for prenatal diagnosis of homozygous alpha-thalassemia-1. With this technique, invasive prenatal testing and complications can be avoided in 79.2% of unaffected fetuses. © 2011 John Wiley & Sons, Ltd.