Via Research Recognition Day 2024 VCOM-Carolinas

Clinical Case-Based Reports

Positives and Negatives A Case of Weak Rh Typing as Pertaining to Pregnancy Nicole Villa OMS-III 1, Jordan Winebrenner OMS-III 1 Lindsay Tjiattas-Saleski DO 1 Edward Via College of Osteopathic Medicine-Carolinas Campus, Spartanburg, SC 1 PRISMA Health Greenville, SC 2

Abstract

Initial Presentation

Discussion

A 28-year-old G3P2 female presented to the emergency department (ED) with vaginal bleeding. A spontaneous and complete abortion was confirmed. The patient noted that she had come to the ED for RhoGAM administration as she noted previously testing as Rh-. However, her blood type during this visit tested as Rh+. After consultation with Obstetrics and Gynecology, RhoGAM was administered with the intention to protect future pregnancy attempts.

Acknowledgements • ACOG recommends providers give RhoGAM to individuals exhibiting a weak D blood type. This recommendation aligns with the rationale applied to the Rh D typing of blood donors. Recommendations: • Further data and research are needed to help answer these questions and create better guidelines in the future. Final Diagnosis – "Weakly Rh+" or "Weak D" Considerations: • Some literature suggests that weakly Rh+ women might not require RhoGAM, the theory being that these patients possess enough of the Rh+ antigen to prevent alloimmunization from occurring. • Most women who are weakly Rh+ have one of the more common genotypes to safely not need RhoGAM. • There are documented cases showing weak Rh+ genotypes that produce anti-Rh antibodies, leading to alloimmunization. • If administered within 72 hours of delivery, incidence of Rh alloimmunization decreases from 13% to 2%. • Only a genetic test can tell which genotype of the Rh gene the patients possess. Treatment Options: • Giving RhoGAM is generally thought to be the safest option. • Should balance safety versus the potential for medical waste in cases where it might not be essential. • Risks of RhoGAM administration - site reaction, renal insufficiency, anaphylaxis, anemia, etc.

Introduction Rh alloimmunization becomes a concern when an Rh- mother produces antibodies that traverse the placenta, reacting against her Rh+ fetus. The highest risk typically arises when an Rh- mother has previously experienced an Rh+ pregnancy and was exposed to the Rh+ antigen during delivery. In subsequent pregnancies, the mother's body generates class-switched IgG antibodies capable of crossing the placenta, potentially causing Hemolytic Disease of the Newborn. Presently, the American College of Obstetricians and Gynecologists (ACOG) recommends blood typing for pregnant women, accompanied by the administration of one dose of RhoGAM at 28 weeks and another at delivery if the baby is confirmed as Rh+. Since the 1970s, RhoGAM treatment has significantly reduced alloimmunization rates by 80-90%. While the current guidelines are well-suited for women with distinctly Rh+ or Rh status, challenges emerge in cases involving women with weakly Rh+. The assessment of Rhesus (Rh) typing plays a crucial role in determining the necessity for Rh immune globulin (RhoGAM) shots. RhoGAM serves as a preventative measure against Rh alloimmunization, commonly referred to as Hemolytic Disease of the Newborn, particularly in Rh-negative (Rh-) women. However, a patient's blood type may not align with the standard Rh+ or Rh- classifications. Some individuals fall under the labels of "weakly Rh+" or "formerly Rh+." This intricacy is evident in the case of a 28 year-old Gravida 3 Para 2 female, whose blood test results display inconsistencies across multiple pregnancies. As there is a noteworthy demographic trend in the United States presenting with an elevated prevalence of Rh+ status among women, it is important to delve into the nuanced aspects of Rh typing, emphasizing its implications for maternal-fetal health and shedding light on the distinctive challenges presented by these variations .

Treatment and Findings

Gestation Initial Blood Result

On Re-check

Rh IG Administered*

G1 G2 G3 G4

O- O-

O+, O-

+ +

O+

+ -

O+

----

+ / + +

Weak O+

Weak O+

*+ indicates 1 dose of IVIg, - indicates no dose, / indicates N/A The 1st symbol represents the 1st dose of anti-Rh Ig, second symbol represents the second dose

• It is estimated that up to 1% of Caucasian women express a genotype of the Rh gene that is classified as "weak D" or "weakly Rh+". • About 80% of these women have a genotype that will not lead to Rh alloimmunization because they produce enough of the Rh antigen to not illicit a reaction against the fetus. • 20% of women in this category have a genotype that could possibly cause Rh-alloimmunization. • Guidelines from ACOG and the American Association of Blood Banks (AABB) conflict on how to treat these women. • The only definitive method of determining what type of weak Rh+ genotype patients have is to perform RhD genotyping. This patient has not received genetic testing, and because there is a potential risk of alloimmunization of the baby, both OBGYN and hematology-oncology have decided to manage her as if she were Rh-.

References

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2024 Research Recognition Day