From the Guidelines
The Rh factor is a protein found on the surface of red blood cells in most people, and its presence or absence can significantly impact the fetus or newborn, particularly if an Rh-negative mother carries an Rh-positive fetus, potentially leading to hemolytic disease of the newborn (HDN) in subsequent pregnancies. The Rh factor becomes crucial during pregnancy because if the mother's blood comes into contact with the baby's blood, her immune system may recognize the Rh protein as foreign and produce antibodies against it 1. While this usually doesn't affect a first pregnancy, these antibodies can cross the placenta in subsequent pregnancies with Rh-positive babies, attacking the fetus's red blood cells and causing HDN, which can lead to anemia, jaundice, brain damage, or even death of the fetus or newborn.
To prevent this, Rh-negative pregnant women typically receive RhoGAM (Rh immunoglobulin) injections at around 28 weeks of pregnancy and within 72 hours after delivery of an Rh-positive baby, as this has been shown to significantly reduce the risk of RhD alloimmunization and its adverse perinatal outcomes 1. The use of RhD immune globulin (RhIg) has been highly effective in reducing the burden of perinatal morbidity and mortality attributable to RhD alloimmunization, with studies indicating that a postpartum dose of RhIg decreases the rate of postpartum anti-D alloimmunization from between 13% and 17% to 1% to 2% 1.
Key points to consider include:
- The importance of determining the blood type and Rh status of all pregnant women early in pregnancy to identify and manage the potential risk associated with the Rh factor.
- The administration of RhIg in Rh-negative women after spontaneous or induced abortion at less than 12 weeks of gestation, with a recommended dose of 50 mg within 72 hours of the event, or a 300 mg dose if the lower dose is unavailable 1.
- The potential for resource over-utilization with RhIg administration and the need for prioritization of postpartum patients and antenatal patients at later gestational ages when the supply of RhIg is limited 1.