How does being Rh (Rhesus) negative impact a pregnant patient's pregnancy?

From the Guidelines

Rh negative pregnant patients should receive RhoGAM (Rh immunoglobulin) at 28 weeks of pregnancy and again within 72 hours after delivery if the baby is Rh positive to prevent Rh incompatibility and its associated risks, as supported by the most recent evidence from 2024 1. The standard dose is 300 micrograms intramuscularly. Additional doses may be needed after potentially sensitizing events like miscarriage, abortion, ectopic pregnancy, or invasive procedures.

• Blood typing and antibody screening are essential early in pregnancy to identify Rh status.
• If sensitization has already occurred (positive antibody screen), the pregnancy requires close monitoring with serial ultrasounds and possibly middle cerebral artery Doppler studies to assess for fetal anemia.
• The preventive approach with RhoGAM is highly effective, blocking the mother's immune response to Rh positive blood cells and preventing antibody formation that could harm future pregnancies, as demonstrated by a significant reduction in perinatal morbidity and mortality attributable to RhD alloimmunization 1. Key considerations include:
• The risk of RhD alloimmunization arising from spontaneous or induced abortion at <12 weeks of gestation is low but not negligible, and prevention is critical to avoid adverse perinatal outcomes 1.
• The Society for Maternal-Fetal Medicine recommends offering both RhD testing and RhIg administration for spontaneous and induced abortion at <12 weeks of gestation, given the substantial impact of alloimmunization on pregnancy and perinatal outcomes 1.
• The risks associated with RhIg administration are low, and the benefits of prevention outweigh the risks, as supported by the evidence from 2024 1.

From the FDA Drug Label

RhoGAM is used in pregnant women for the suppression or Rh isoimmunization. The available evidence suggests that Rho(D) Immune Globulin (Human) does not harm the fetus or affect future pregnancies or reproduction capacity when given to pregnant Rh0(D)-negative women for suppression of Rh isoimmunization.

The administration of RhoGAM to an Rh-negative pregnant patient can impact her pregnancy by preventing Rh immunization. This is crucial in preventing the formation of antibodies against Rh-positive red blood cells, which can lead to hemolytic disease of the newborn in future pregnancies.

• Key benefits:
  • Prevents Rh immunization
  • Does not harm the fetus
  • Does not affect future pregnancies or reproduction capacity
• Administration: RhoGAM is administered at 28 weeks of gestation and within 72 hours of delivery to Rh-negative pregnant women carrying an Rh-positive fetus.

2 and 2

From the Research

Impact of Rh Negative Pregnancy on the Patient

• An Rh negative pregnant woman can be affected by her pregnancy in several ways, primarily due to the risk of Rh alloimmunization 3, 4.
• Rh alloimmunization occurs when an Rh negative woman is exposed to Rh positive blood, which can happen during pregnancy, childbirth, or blood transfusion.
• To prevent Rh alloimmunization, anti-D immune globulin (RhIG) is administered to Rh negative women during pregnancy and after childbirth 3, 4.

Administration of RhIG

• The guidelines for the administration of RhIG vary depending on the gestational age and the presence of fetomaternal hemorrhage (FMH) 3.
• Anti-D Ig 300 microg is recommended to be given to Rh negative women at 28 weeks' gestation and within 72 hours of delivery if the baby is Rh positive 3.
• Additional anti-D Ig may be required if there is a significant FMH, and the dose is calculated based on the amount of fetal red blood cells in the maternal circulation 3, 4.

Risks and Complications

• The risk of Rh alloimmunization is higher in women who have had previous pregnancies or blood transfusions 4.
• If an Rh negative woman is not given RhIG during pregnancy or after childbirth, she may develop anti-D antibodies, which can cause hemolytic disease of the newborn in future pregnancies 3, 4.
• New laboratory procedures and changes in Rh blood typing methods can affect a woman's candidacy for RhIG and may require re-evaluation of her blood type 5.

Current Practices and Guidelines

• Current guidelines recommend the use of RhIG immunoprophylaxis after RhD-positive red cell exposure in RhD-negative patients via transfusion 6.
• However, a survey of AABB-accredited transfusion services in the US found that approximately half of the respondents had policies on RhIG administration after RhD-incompatible transfusions, while others had no written policies or inadequate safeguards to mitigate the risk of hemolysis associated with high-dose RhIG 6.
• The use of RhIG has dramatically decreased the incidence of hemolytic disease of the fetus and newborn, but instances of Rh immunization continue to occur due to failure to administer RhIG when indicated or in the appropriate dose 4.