Two unusual cases of haemoglobin Bart’s hydrops fetalis screened negative on universal prenatal screening for thalassaemia

In universal prenatal screening for alpha thalassemia, if mean corpuscular volume (MCV) of a women is low (<80fL) but her partner's MCV is normal, her pregnancy is considered not at risk of haemoglobin (Hb) Bart's disease. Here, we report two rare cases of fetal Hb Bart's disease which illustrate an exception. Case 1: A 34-year-old, G3P2, Chinese woman had a low MCV (69.1 fL) due to alpha thalassemia trait. Her husband's MCV was normal. Routine scan at 21 weeks showed fetal hydrops with ascites, bilateral pleural effusions, cardiomegaly, and increased middle cerebral artery peak systolic velocity (MCAPSV) (52.3cm/s, >1.55MoM). Cordocentesis showed Hb of 4.7g/dL, and Hb Bart's disease. As the couple kept the pregnancy, four in-utero transfusions were given in interval. The baby was delivered by emergency Caesarean section at 31 weeks who required regular blood transfusions after birth and waited for bone marrow transplantation. Investigations showed fetal Hb Bart's disease from maternal uniparental disomy (UPD) 16. Case 2: A 21-year-old, G2P0, Chinese woman was referred to our hospital for management of fetal hydrops at 31 weeks. She had a low MCV (76 fL) related to Hb E while her husband's MCV was normal. Ultrasound examination showed fetal ascites, cardiomegaly but normal MCAPSV (51.4cm/s). Cordocentesis showed Hb of 7.3g/dL. As fetal echocardiography showed features suggestive of near complete premature closure of foramen ovale, emergency Caesarean section was performed two days later. A baby girl of 1.48kg was delivered, but succumbed shortly after birth despite active resuscitation. Subsequent hematological and DNA studies showed Hb Bart's disease, maternal alpha thalassaemia trait coinheritance with Hb E, and a possibility of non-paternity. If midtrimester anomaly scan shows fetal cardiomegaly or hydrops in a woman with low MCV but normal paternal MCV, obstetricians should remain alert for fetal Hb Bart's disease, be it due to rare occurrence of maternal UPD or non-paternity.link_to_OA_fulltex