Alpha thalassemia major or hemoglobin BHFS is thought to be incompatible of life. A prevalence study conducted in Hong Kong showed 4.6% of the screened population are heterozygous carriers of deletional type alpha thalassemia, who would have 25% risk of conceiving fetuses with BHFS if both couple are carrier. Fetuses with BHFS often develop severe anaemia in utero, feature with cardiomegaly, high peak systolic velocity in middle cerebral artery (MCA PSV), thickened placenta, and eventually hydrops, which can lead to intrauterine fetal demise or early neonatal death; while the mother may also be at risk of maternal mirror syndrome which will cause significant morbidity and even mortality. As a result, when the foetuses are diagnosed with BHFS, most couple will terminate the pregnancy.~With the advance of technology, if the couples are both known to be alpha thalassemia carrier (alpha-alpha couples), they may consider pre-implantation genetic diagnosis. However, even though preimplantation genetic testing for monogenic disease (PGT-M) is a mature technique over the decades, it is still technically challenging, requires assisted reproductive technology even if the couple are fertile and relative costly. As a result, most of the alpha-alpha couples still conceive naturally. Prenatal ultrasonic surveillance is usually offered for the couples and prenatal diagnosis is required for genetic analysis to confirm BHFS when there is ultrasound feature of fetal anaemia.~Thus, the investigators propose this pilot study to determine whether in-utero hematopoietic stem cell transplantation for fetuses with confirmed alpha thalassemia major at the time of IUT of red blood cells could be feasible in Hong Kong.
This is a prospective observational pilot study on pregnant women who are diagnosed to have Bart's hydrops fetalis syndrome (BHFS) affected fetuses and opt for continuation of pregnancy will be invited to consider undergoing in-utero hematopoietic stem cell transplantation under a research protocol, aiming to determine whether in-utero hematopoietic stem cell transplantation (HSCT) for fetuses with confirmed BHFS at the time of in-utero transfusion (IUT) of red blood cells could be feasible in Hong Kong. The participants will undergo bone marrow or peripheral blood stem cells harvest and an IUT combined with maternal stem cells.