Introduction to Rh Incompatibility

Rh incompatibility is a condition that occurs when a pregnant woman has Rh-negative blood and her fetus has Rh-positive blood. This blood type incompatibility can lead to serious complications if maternal antibodies cross the placenta and attack the fetus’s red blood cells.

Understanding Rh incompatibility is crucial for nursing care of pregnant women, as early detection and prevention are key to avoiding serious consequences for the fetus and newborn.

Pathophysiology of Rh Incompatibility

The Rh Factor

The Rhesus (Rh) factor is a protein found on the surface of red blood cells. Individuals with this protein are classified as Rh-positive, while those without it are Rh-negative. The Rh factor is inherited genetically.

Mechanism of Sensitization

Rh incompatibility occurs when an Rh-negative mother carries an Rh-positive fetus. Under normal circumstances, maternal and fetal circulations are separate. However, small amounts of fetal blood may enter the maternal circulation during:

• Childbirth or cesarean delivery
• Miscarriage or abortion
• Ectopic pregnancy
• Invasive prenatal testing (amniocentesis, CVS)
• Abdominal trauma
• External cephalic version (turning the baby from breech position)
• Antepartum hemorrhage

Immune Response

When fetal Rh-positive red blood cells enter the Rh-negative mother’s circulation, her immune system recognizes the Rh antigen as foreign and produces anti-Rh (anti-D) antibodies. This process is called alloimmunization or sensitization.

First vs. Subsequent Pregnancies

In most cases, the first Rh-positive pregnancy in an Rh-negative mother does not pose significant risk to the fetus because:

• Initial sensitization typically occurs during delivery
• The primary immune response is slow, producing mainly IgM antibodies that cannot cross the placenta
• By the time IgG antibodies form, the pregnancy is over

In subsequent Rh-positive pregnancies, the risks increase significantly:

• The mother’s immune system mounts a rapid secondary response
• IgG anti-D antibodies cross the placenta and attach to fetal Rh-positive red blood cells
• This leads to hemolysis (destruction) of fetal RBCs
• The severity increases with each subsequent Rh-positive pregnancy

Clinical Presentation of Rh Incompatibility

Maternal Presentation

The mother typically shows no symptoms related to Rh incompatibility. The condition primarily affects the fetus and newborn.

Fetal Presentation

The severity of fetal presentation varies depending on the degree of hemolysis:

Neonatal Presentation (Hemolytic Disease of the Newborn)

Newborns affected by Rh incompatibility may present with:

• Anemia: Pallor, tachycardia, poor feeding
• Jaundice: Due to increased bilirubin from RBC breakdown, typically presents within 24 hours of birth (earlier than physiologic jaundice)
• Hepatosplenomegaly: Enlarged liver and spleen due to increased production of RBCs and filtering of damaged cells
• Hyperbilirubinemia: Elevated bilirubin levels that may lead to kernicterus (bilirubin encephalopathy) if untreated
• Hydrops fetalis: Severe edema, ascites, pleural effusions (in severe cases)
• Petechiae: Due to thrombocytopenia

Long-term Complications

Untreated or severe Rh incompatibility can lead to:

• Kernicterus: Permanent neurological damage from high bilirubin levels
• Cerebral palsy
• Hearing loss
• Developmental delays
• Death (in severe untreated cases)

Diagnosis of Rh Incompatibility

Prenatal Screening

Early identification of at-risk pregnancies is critical for preventing complications of Rh incompatibility.

Monitoring Sensitized Pregnancies

If a mother has already developed anti-D antibodies, additional monitoring is required:

• Antibody titers: Measured every 2-4 weeks to assess risk
  • Critical titer: Usually 1:16 or 1:32 (varies by laboratory)
  • Titers above critical level suggest increased risk of fetal anemia
• Middle Cerebral Artery Peak Systolic Velocity (MCA-PSV): Non-invasive ultrasound measurement used to detect fetal anemia
  • Increased velocity indicates anemia (fetus compensating with hyperdynamic circulation)
  • Values >1.5 multiples of median (MoM) suggest moderate to severe anemia
• Serial ultrasounds: To detect signs of hydrops fetalis
  • Ascites
  • Pleural/pericardial effusions
  • Skin edema
  • Placental thickening
  • Polyhydramnios
• Amniocentesis: Used historically to measure amniotic fluid bilirubin levels (ΔOD450), but now largely replaced by MCA-PSV measurements
• Cordocentesis: Direct sampling of fetal blood to measure hemoglobin levels (invasive, used when MCA-PSV results are inconclusive)

Neonatal Diagnosis

After birth, the following tests are used to diagnose hemolytic disease of the newborn:

• Direct Coombs test (DAT): Detects antibodies bound to the surface of the newborn’s RBCs
• Blood type and Rh factor: Confirms the newborn is Rh-positive
• Complete blood count (CBC): Evaluates anemia (hemoglobin/hematocrit)
• Reticulocyte count: Usually elevated due to increased RBC production
• Bilirubin levels: Total and direct (unconjugated) bilirubin to assess severity of hyperbilirubinemia
• Peripheral blood smear: May show nucleated RBCs, spherocytes, and other abnormal RBC morphology

Management of Rh Incompatibility

Prenatal Management of Sensitized Pregnancies

Once a pregnant woman is sensitized (has developed anti-D antibodies), management focuses on monitoring and treating the fetus:

• Regular monitoring of antibody titers and fetal wellbeing
• Intrauterine transfusion (IUT): The primary treatment for severe fetal anemia
  • Performed when MCA-PSV indicates significant anemia
  • Typically administered into the umbilical vein under ultrasound guidance
  • Provides Rh-negative RBCs to the fetus
  • May need to be repeated every 2-4 weeks until delivery
• Timing of delivery:
  • Mild cases: May continue to term (37-38 weeks)
  • Severe cases requiring IUT: Usually delivered by 35-37 weeks after lung maturity is confirmed
  • Critical cases: Early delivery may be necessary, balancing risks of prematurity against risks of continued intrauterine exposure to antibodies

Neonatal Management

Management of the affected newborn depends on the severity of hemolytic disease:

Nursing Considerations in Management

Nursing care is critical in both prenatal and neonatal management:

• Prenatal care:
  • Educating the mother about the condition and monitoring process
  • Providing emotional support
  • Assisting with fetal monitoring
  • Preparing for intrauterine transfusions
• Neonatal care:
  • Close monitoring of vital signs
  • Frequent assessment for signs of anemia and jaundice
  • Proper positioning during phototherapy
  • Eye protection during phototherapy
  • Temperature regulation
  • Adequate hydration
  • Monitoring intake and output
  • Observing for complications
• Family support:
  • Education about the condition and treatment plan
  • Promoting parent-infant bonding despite medical interventions
  • Addressing concerns about long-term outcomes

Prevention of Rh Incompatibility

Prevention is the cornerstone of managing Rh incompatibility. Since the introduction of RhIg (Rh immune globulin) in the late 1960s, the incidence of Rh sensitization has decreased dramatically.

RhIg (RhoGAM) Administration

RhIg is a blood product containing IgG anti-D antibodies that works by binding to any fetal Rh-positive cells in the maternal circulation, preventing them from triggering the mother’s immune system to produce antibodies.

Indications and Timing for RhIg

RhIg should be administered to Rh-negative, non-sensitized women in the following situations:

Nursing Considerations for RhIg Administration

• Verification:
  • Confirm mother is Rh-negative
  • Confirm absence of anti-D antibodies before administration
  • After delivery, verify infant is Rh-positive before administering RhIg
• Administration:
  • Administer intramuscularly in the deltoid or ventrogluteal site
  • Never administer intravenously
  • Observe for 20 minutes after administration for allergic reactions
• Documentation:
  • Record lot number, dose, site, time, and patient response
  • Document patient education provided
• Patient education:
  • Explain purpose of RhIg
  • Inform about potential side effects (soreness at injection site, mild fever)
  • Emphasize importance of receiving RhIg for all indicated events in current and future pregnancies

Monitoring After Large Fetomaternal Hemorrhage

After delivery, a Kleihauer-Betke test or flow cytometry may be performed to quantify the volume of fetomaternal hemorrhage. If the hemorrhage is large, additional doses of RhIg may be required (one standard dose covers approximately 30 mL of fetal blood).

Best Practices & Nursing Updates for Rh Incompatibility

Current Best Practices

Recent Updates in Nursing Care

Several important updates have emerged in the nursing care of patients with Rh incompatibility:

• Universal screening protocols: All pregnant women should receive ABO/Rh screening at first prenatal visit, with antibody screening for Rh-negative women.
• Electronic medical record alerts: Implementation of EMR alerts to ensure timely administration of RhIg for eligible patients.
• Extended window for RhIg effectiveness: While administration within 72 hours is optimal, RhIg may provide some protection when given up to 10-14 days after potential sensitization events.
• Reduced-dose protocols: Some centers are adopting reduced-dose RhIg protocols for early pregnancy events (<12 weeks) to conserve resources while maintaining efficacy.

Nursing Role in Prevention

Nurses play a crucial role in preventing Rh incompatibility complications:

• Education: Educate Rh-negative women about the importance of RhIg prophylaxis and when to seek care for events that may cause fetomaternal hemorrhage.
• Documentation: Maintain accurate records of blood type, antibody screening results, and RhIg administration.
• Communication: Ensure proper handoffs between care settings to prevent missed opportunities for RhIg administration.
• Advocacy: Advocate for timely administration of RhIg when indicated.
• Risk management: Identify and flag Rh-negative patients for special attention during pregnancy and delivery.

References

1. Pegoraro, V., Urbinati, D., Visser, G.H.A., et al. (2020). Hemolytic disease of the fetus and newborn due to Rh(D) incompatibility: A preventable disease that still produces significant morbidity and mortality in children. PLoS ONE, 15(7), e0235807. https://doi.org/10.1371/journal.pone.0235807
2. American College of Obstetricians and Gynecologists. (2017). ACOG Practice Bulletin No. 181: Prevention of Rh D Alloimmunization. Obstetrics & Gynecology, 130(2), e57-e70.
3. Harrod, K.S., Hanson, L., VandeVusse, L., et al. (2003). Rh negative status and isoimmunization update: A case-based approach to care. Journal of Perinatal & Neonatal Nursing, 17(3), 166-180.
4. Fung, K.F.K., Wong, K., Walsh, J., et al. (2024). Guideline No. 448: Prevention of Rh D alloimmunization. Journal of Obstetrics and Gynaecology Canada. https://www.sciencedirect.com/science/article/pii/S1701216324002603
5. de Haas, M., Thurik, F.F., Koelewijn, J.M., et al. (2015). Haemolytic disease of the fetus and newborn. Vox Sanguinis, 109(2), 99-113.
6. Cleveland Clinic. (2023). Rhesus (Rh) Factor: Incompatibility, Complications & Pregnancy. https://my.clevelandclinic.org/health/diseases/21053-rh-factor
7. RegisteredNurseRN.com. (2018). Rh Incompatibility in Pregnancy NCLEX Review. https://www.registerednursern.com/rh-incompatibility-pregnancy-nclex-review/
8. Lecturio Nursing. (2024). Rh Incompatibility [+ Free Cheat Sheet]. https://www.lecturio.com/nursing/free-cheat-sheet/rh-incompatibility-in-pregnancy/