Prenatal Care for Rh-Positive Patient Planning Second Pregnancy
An Rh-positive patient attempting a second pregnancy does not require anti-D immunoglobulin (RhIG) prophylaxis, as she cannot develop anti-D antibodies against the Rh antigen she already possesses. 1
Key Principle: Understanding Rh Status
- Rh-positive individuals (those with the D antigen) are not at risk for Rh alloimmunization and should never receive anti-D immunoglobulin, as they already express the D antigen on their red blood cells 2, 3
- Women with "weak D" (also known as Du-positive) should similarly not receive anti-D, as they are considered Rh-positive 2
Standard Prenatal Care Recommendations
Blood Type and Antibody Screening
- All pregnant women (D-negative or D-positive) should undergo blood typing and screening for alloantibodies with an indirect antiglobulin test at the first prenatal visit and again at 28 weeks' gestation 2
- This screening detects other clinically significant antibodies (such as anti-Kell, anti-c, anti-E) that can cause hemolytic disease of the fetus and newborn, even in Rh-positive mothers 2
Important Caveat: Laboratory Method Changes
- Be aware that new molecular blood-typing methods have identified variant D antigens, which may be reported differently depending on the laboratory method used 4
- If a woman was previously typed as Rh-negative in a prior pregnancy but now tests as Rh-positive (or vice versa), this may reflect changes in laboratory procedures rather than an actual change in blood type 4
- Women with partial D antigens may be reported as Rh-negative and would require RhIG prophylaxis 4
No Special Rh-Related Interventions Required
Since this patient is Rh-positive:
- No routine antenatal RhIG at 28 weeks' gestation 1, 2
- No postpartum RhIG administration 1
- No RhIG following potentially sensitizing events (amniocentesis, chorionic villus sampling, abortion, trauma, etc.) 2
Focus on Other Prenatal Care Priorities
For a second pregnancy in an Rh-positive patient, standard prenatal care should focus on:
- Routine antibody screening to detect non-Rh antibodies that could affect the fetus 2
- Standard obstetric monitoring based on maternal age, medical history, and pregnancy-specific risk factors
- Assessment for complications from the first pregnancy that might recur
The absence of Rh-negative status eliminates the entire cascade of RhIG prophylaxis protocols that would otherwise be necessary throughout pregnancy and postpartum. 1, 3