Authors (including presenting author) :
Hui PW (1), P Pang (1), M Tang (1)
Affiliation :
Department of Obstetrics & Gynaecology, Queen Mary Hospital
Introduction :
Couples who are carriers of heterozygous alpha0 thalassaemia carry 25% chance of having foetuses affected by Haemoglobin (Hb) Bart’s hydrops foetalis syndrome (BHFS). Antenatal treatment with intrauterine transfusion (IUT) to correct in-utero anaemia has been attempted with success for foetuses with Hb Bart’s disease. BHFS is no longer considered as invariably lethal.
Universal antenatal screening of thalassaemia was implemented since 2000 in Hong Kong. Haemoglobin electrophoresis would be performed for couples having mean corpuscular volume below 80 fL. Couples at risk would be offered options of prenatal ultrasound surveillance for cardiomegaly, placentomegaly and elevated peak systolic velocity of middle cerebral artery or invasive tests. Diagnosis of BFHS was confirmed by genetic study.
Objectives :
To review prenatal diagnosis and outcome of alpha thalassaemia major through 20 years of universal antenatal screening
Methodology :
Clinical data of all couples at risk of BHFS who attended for prenatal diagnosis at Tsan Yuk Hospital from January 2000 to December 2019 were retrieved for analysis. Information on demographic data, ultrasound findings, invasive tests, prenatal diagnosis, in-utero intervention, pregnancy outcomes and postnatal course of Hb Bart’s babies was reviewed.
Result & Outcome :
There were 390 at risk foetuses from 373 pregnancies (357 singletons, 15 twins and one triplet). Excluding 10 miscarriages and one termination for unwanted pregnancy, prenatal diagnosis was provided for 379 pregnancies.
Over 80% (304/379) pregnancies was monitored by ultrasound and 53 of them ultimately required invasive diagnostic procedures where 41 procedures were performed for suspected foetal anaemia. Presence of hydrops foetalis, limb reduction, tricuspid regurgitation and pleural effusion was totally predictive of BFHS. The negative predictive value was 99.2% for cardiomegaly and 97.0% for placentomegaly. The sensitivity of cardiomegaly was 93.8%, but the overall sensitivity with any ultrasound abnormality was 100% and no foetuses with BFHS was missed. There were 30 BHFS diagnosed from this pathway giving a diagnostic yield of 73%. Another 35 foetuses with BHFS were diagnosed from couples who opted to have invasive tests.
Three women with foetuses affected by BHFS continued pregnancy where IUT was performed. None of the foetus was hydropic at the time of diagnosis. The gestational age of first transfusion was 20-21 weeks with pre-transfusion haemoglobin level of 6.2-6.9 g/dL. All babies were born with satisfactory Apgar scores with haemoglobin level of at least 12 g/dL, and treated with regular transfusions afterwards. All received haematopoietic stem cell transplant in childhood and became transfusion independent.
