Ultrasonographic prediction of homozygous α 0-thalassemia using placental thickness, fetal cardiothoracic ratio and middle cerebral artery Doppler: Alone or in combination?

Abstract

Objective To compare the predictive values of three ultrasonographic parameters: placental thickness (PT), fetal cardiothoracic ratio (CTR) and middle cerebral artery peak systolic velocity (MCA-PSV), alone or in combination, in pregnancies affected by homozygous α 0- thalassemia at 12-20 weeks' gestation. Methods: Pregnant women at risk of carrying a fetus affected by homozygous α 0-thalassemia were studied from 1995 to 2006 using serial ultrasonography at 12-15 weeks, 16-20 weeks and 30 weeks' gestation. We measured CTR and PT from 1995, and MCAPSV as well from 1997. An invasive prenatal test was offered if cardiomegaly with or without placentomegaly was detected but the MCA-PSV results were used only retrospectively for analysis. Results: Of a total of 777 at-risk fetuses studied, 138 (17.8%) were affected by homozygous a0-thalassemia. At 12-15 weeks' gestation, 598 ultrasound examinations were performed. CTR was better than both PT and MCAPSV in the prediction of affected pregnancies. The highest sensitivity (98.3%) was achieved by the combination of CTR and/or MCA-PSV at a false-positive rate of 15.8%. At 16-20 weeks' gestation, 410 ultrasound examinations were performed, 121 of which were at the patient's first visit and 289 of which were at a follow-up visit. Both CTR and MCA-PSV predicted the affected pregnancies equally well. The sensitivity of CTR was 100.0%, but the false-positive rate was 5.2%. In contrast, the false-positive rate of MCA-PSV alone was 1.4% and that of the combination of CTR and MCA-PSV was 0%, although their sensitivities were less than 65%. Conclusions: The data suggest that adding MCA-PSV to CTR in the prediction of homozygous α 0- thalassemia can increase the sensitivity at 12-15 weeks and decrease the false-positive rate at 16-20 weeks' gestation. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.