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Prenatal diagnosis of haemoglobin Bart's disease by cordocentesis at 12-14 weeks' gestation
1Department of Obstetrics and Gynaecology, University of Hong Kong, Tsan Yuk Hospital, Hong Kong.
Insights
Prenatal diagnosis for haemoglobin Bart's disease can be improved. Ultrasound findings of enlarged placenta and fetal heart at 12-14 weeks can identify affected pregnancies for cordocentesis and Hb study.
Area of Science:
- Maternal-fetal medicine
- Prenatal diagnostics
- Genetics
Background:
- Alpha-thalassaemia-1 carriers have a 25% risk of fetal haemoglobin (Hb) Bart's disease.
- Conventional prenatal diagnosis via DNA studies is costly and time-consuming.
Purpose of the Study:
- To evaluate ultrasound markers for early detection of Hb Bart's disease.
- To assess cordocentesis and Hb study as an alternative diagnostic approach.
Main Methods:
- Abdominal ultrasound at 12-14 weeks to identify placentomegaly and cardiomegaly (cardiothoracic ratio > 0.5).
- Free-hand cordocentesis using a 26-gauge spinal needle with a 20-gauge introducer.
- Hb electrophoresis for confirmation.
Main Results:
- Ultrasound identified 11 affected pregnancies.
- Successful cordocentesis in 10 cases; Hb Bart's disease confirmed by electrophoresis.
- One procedure failed with a smaller needle; Hb study post-abortion confirmed disease.
Conclusions:
- Concomitant placentomegaly and cardiomegaly on ultrasound (12-14 weeks) are highly specific for Hb Bart's disease.
- Cordocentesis and Hb study offer a valuable alternative prenatal diagnostic method, especially where molecular studies are limited.
Abstract:
Couples with alpha-thalassaemia-1 face a 25 per cent risk of having fetuses with haemoglobin (Hb) Bart's disease. Prenatal diagnosis is conventionally performed by DNA studies of chorionic villi or amniocytes obtained from chorionic villus biopsy or amniocentesis. DNA studies are expensive and time-consuming. We identified 11 affected pregnancies on abdominal ultrasound examination at 12-14 weeks when the placental thickness exceeded the mean plus 2 SD measurement for the gestational week and the cardiothoraic ratio was more than 0.5. Cordocentesis was then performed with a free hand technique. The procedures were successful in ten cases using a 26-gauge spinal needle with a 20-gauge introducer. Hb Bart's disease was confirmed in all cases by Hb electrophoresis. The procedure was unsuccessful in one case when a 22-gauge spinal needle was used. Hb study of fetal blood collected at abortion also confirmed Hb Bart's disease. In conclusion, ultrasound findings of concomitant placentomegaly and cardiomegaly at 12-14 weeks is highly specific of disease in pregnancies at risk of Hb Bart's disease. Cordocentesis and Hb study in pregnancies with these sonographic manifestations may be an alternative prenatal diagnostic approach. This diagnostic approach is of particular value in areas where resources for molecular studies are limited.