Prenatal ultrasonographic prediction of homozygous type 1 α-thalassemia at 12 to 13 weeks of gestation, ,

We determined the feasibility of prenatal prediction of type 1 homozygous α-thalassemia at 12 to 13 weeks of gestation by either abdominal or vaginal (or both) ultrasonographic examination to measure the fetal cardiothoracic ratio in 135 at-risk pregnancies. Forty-three fetuses were affected by homozygous type 1 α-thalassemia. The mean cardiothoracic ratio was significantly larger than that of the unaffected fetuses (0.54 vs 0.45, P< .0005), with no overlap between the 2 groups. A cardiothoracic ratio cutoff point of ≥0.5 was 100% sensitive and specific for disease. (Am J Obstet Gynecol 1999;180:148-50.)