Non-invasive prenatal detection of haemoglobin Bart's disease by cardiothoracic ratio during the first trimester.

OBJECTIVE

To evaluate the efficacy of the sonographic cardiothoracic ratio (CTR) in early pregnancy for the prediction of fetal haemoglobin (Hb) Bart's disease.

STUDY

DESIGN

Over a 1.5-year period at a Chinese tertiary obstetric centre, women at risk of Hb Bart's disease were given the option of a non-invasive approach to exclude an affected pregnancy between 11 weeks and 13 weeks and 6 days of gestation, with a routine rescan after a 2-week interval. The fetal CTR, a sonographic marker, was assessed, and invasive testing followed in cases of fetal cardiomegaly. The diagnosis of fetal Hb Bart's disease was based on DNA analysis from chorionic villus sampling.

RESULTS

Of 154 at-risk cases studied, five cases (four at 11 weeks of gestation) were subjected to direct invasive testing because of an unsatisfactory scan. Of the remaining 149 cases, non-invasive ultrasound examinations were performed successfully. Thirty-four (22.8%) affected pregnancies were revealed, including one picked up on rescan. The sensitivity and specificity of the non-invasive approach were 97.1% and 100%, respectively. The need for an invasive test was reduced by 74.7%, and all affected pregnancies except one were diagnosed before 14 weeks of gestation.

CONCLUSION

CTR can differentiate reliably between pregnancies with and without Hb Bart's disease. This non-invasive approach for the exclusion of Hb Bart's disease can be used in early pregnancy.