Determination of Fetal Blood Group by Next-Generation Sequencing - A Clinical Study in Pregnancies with Maternal Alloantibodies Directed Against Fetal Blood Cells (Alloimmunization During Pregnancy)

Maternal antibodies can cross the placenta and reach the fetus during pregnancy. In some cases, these antibodies are harmful to the fetus. One such condition is alloimmunization against fetal red blood cells or platelets. This occurs in approximately 1% of all pregnancies and, if left undetected, unmonitored, and untreated, may lead to fetal anemia, heart failure, bleeding, or fetal death.

Today, pregnant women are offered screening for antibodies against red blood cells during pregnancy. It is the fetus that may be affected, making the fetus the patient whose risk of disease and complications after birth healthcare aims to identify and minimize. This presents a particular challenge because, until birth, the fetus remains physically connected to and dependent on the pregnant woman.

Methods are available to estimate the fetal blood group and thereby assess the risk to the unborn child. Since the fetus inherits its blood group from both biological parents, some fetuses will carry blood group antigens that are targeted by the mother's antibodies, while others will not. Current methods are imperfect, and in approximately 30% of cases the fetus will not carry the relevant blood group antigen. Consequently, many pregnancies undergo unnecessary monitoring, causing additional healthcare costs as well as anxiety for the pregnant woman and her partner.

Using advanced genetic technology, we aim to investigate whether analysis of a maternal blood sample by Next-Generation Sequencing (NGS) can accurately determine the fetal blood group. This would enable reliable identification of fetuses at risk of being affected by maternal alloantibodies, while also identifying those that are not at risk and therefore do not require unnecessary monitoring. NGS will be used in a study population in Sweden (seven centers) and validated for patient safety, logistic implementation and health economic costs.