Consequences of erroneous reporting and interpretation of positive antibody screen in Rhesus (Rh) negative pregnancy: A report of two cases

Abstract

Background

Rhesus (Rh) D Immunoglobulin (RhIG), (Rhogam®) is indicated for all pregnant Rh-negative women at 28 weeks of gestation followed by a second dose within 72 h after birth if the newborn is Rh-positive and it reduces the risk for Rh alloimmunization of the mother from 13%–16% to 0.1%–0.2%.

Methods

Retrospective review of causes and outcomes of two cases of Rh-induced hemolytic disease of the newborn (Rh-HDN) at our institution.

Results

The determination of passive anti-D from RhIG versus active anti-D from maternal sensitization and subsequent management, relies entirely on a reliable history of prior and timely RhIG administration in the mother.

Conclusion

These two cases illustrate the importance of communication (and the detriment of the lack thereof) between blood bank and maternal—and neonatal care providers in the prevention—and management of Rh-HDN.

Keywords

Rhesus allo-immunization hemolytic disease RhIG

Introduction

The Rhesus (Rh) locus is located on chromosome number one¹ and consists of the D, C, c, E, and e antigens (there is no d) that are expressed on the surface of red blood cells (RBC). Absence of the Rh (D) antigen confers Rh negativity and occurs in 15% of Caucasians, 8% of Blacks, and 1% of Asians.²

Rh alloimmunization occurs in 13% to 16% of pregnancies where an Rh-negative mother is carrying an Rh-positive fetus.³

Rh(D) Immunoglobulin (RhIG) is indicated for all pregnant Rh-negative women at 28 weeks gestation followed by a second dose within 72 h after birth if the newborn is Rh-positive and it reduces the risk for Rh alloimmunization of the mother to 0.1% to 0.2%. Post-partum administration alone reduces the risk to 0.5% to 1.8%. Once a mother is sensitized and develops active anti-D, RhIG confers no benefit.³

Case presentations

Case 1

A 36-year-old Gravida 4 para 3 Abortus 1 (G4P3Ab1) B-negative, antibody screen positive Hispanic mother delivered by Caesarian-section (C/S) at 36 and 6/7 weeks. Apgar scores were 4 and 8 at 1 and 5 min, respectively. The male infant weighed 2745 g.

Prenatal labs at 15 and 2/7 weeks had shown a positive antibody screen and were therefore reported as anti-D (active) since there was no history of prior RhIG administration. The obstetric provider's records at 20 and 5/7 weeks indicated the need for RhIG at 28 weeks and postpartum. RhIG was then ordered by the provider's office at 24 and 5/7 weeks despite the mother being sensitized to the D antigen. Repeat testing by the hospital blood bank at 26 and 6/7 weeks confirmed active anti-D by interviewing the patient and obtaining a negative history for prior RhIG. For unclear reasons, the mother still received RhIG at 28 and 5/7 weeks, the obstetrician was never notified of the active anti-D at 26 and 6/7 weeks and no subsequent antibody titers were followed.

The mother returned to labor and delivery at 36 and 6/7 weeks and the blood bank now mistook the admission positive antibody screen for passive anti-D due to the documentation of having received RhIG at 28 weeks, overlooking the previously reported active anti-D results.

The infant had an elevated transcutaneous bilirubin of 12.4 mg/dL (212.09 µmol/L) at 9 h of age. A confirmatory total serum bilirubin (TSB) was 11.9 mg/dL (203.54 µmol/L) and phototherapy was started by the pediatrician. He was transferred to the neonatal intensive care unit (NICU) once additional laboratory tests showed a hemoglobin of 84 g/L, hematocrit of 26.8%, reticulocyte count of 18.6%, and the blood type being B-positive/Direct Coombs positive. The infant was treated with intensive phototherapy, phenobarbital, received three packed red blood cell (PRBC) transfusions, and three doses of intravenous immunoglobulin (IVIG).

An interview with the mother by the neonatologist revealed that this was her third child and that she has two older children with a different father who were both born in El Salvador. There was no history of severe jaundice in the two older siblings.

The TSB reached a peak level of 13 mg/dL (222.35 µmol/L) and the direct bilirubin 1.7 mg/dL (29.08 µmol/L) but did not reach the threshold for exchange transfusion.⁴

The infant did well and was discharged to home at 23 days of age. Anticipatory guidance emphasizing the high risk of reoccurrence in subsequent pregnancies was given to the family.

Case 2

A 34-year-old G2P2 A-negative, antibody screen-positive Hispanic mother delivered by C/S at 35 and 0/7 weeks due to breech presentation in labor. Apgar scores were 4, 6, and 8 at 1, 5, and 10 min, respectively, and the 2770 g female infant was admitted to the NICU due to respiratory distress. No prenatal records were available for the blood bank which was erroneously told by labor and delivery that the mother had received RhIG 6 weeks earlier and therefore reported her positive antibody screen at that time as passive anti-D.

Upon admission to the NICU, the infant was noted to be bruised, and have mild generalized central edema and palpable hepatosplenomegaly. Chest radiograph showed cardiomegaly (Figure 1). Hemoglobin was 90 g/L, hematocrit 30.2%, reticulocyte count 40%, nucleated red blood cells (nRBC) 1348% of white blood cells (WBC), and platelets 60 × 10⁹/L. Blood type was A-positive/Direct Coombs positive. The serum albumin was low at 1.8 g/dL (18 g/L) and trace ascites was noted on abdominal ultrasound. The neonatologist interviewed the mother who revealed that she received RhIG in Mexico after her first pregnancy but not during the first pregnancy itself. With this information, the blood bank amended the positive antibody screen to active anti-D.

The infant was treated with intensive phototherapy, phenobarbital, received two PRBC transfusions, three platelet transfusions, and eight doses of IVIG. The nRBC count peaked the next day at 1794% of WBC but thereafter gradually normalized. TSB reached a peak level of 17.1 mg/dL (292.48 µmol/L) and the direct bilirubin 11.4 mg/dL (194.99 µmol/L) but never reached the threshold for exchange transfusion.⁴ The infant developed transient skin pigmentation consistent with Bronze baby syndrome as a consequence of phototherapy in the setting of cholestatic jaundice from hemolysis. The direct hyperbilirubinemia was treated with Ursodeoxycholic acid and gradually resolved.

The infant did well and was discharged to home at 38 days of age. Anticipatory guidance emphasizing the high risk of reoccurrence in subsequent pregnancies was given to the family.

Discussion

Once a mother is sensitized and develops active anti-D, RhIG confers no benefit.³ This is what happened in case 1 and also likely in case 2 since this mother received only post-partum RhIG in her prior pregnancy and none in her current.

The mechanism of action for RhIG is the destruction of the fetal Rh-positive red blood cells (RBC) in the mother's circulation prior to an active response from her own immune system. As a result of RhIG administration, a weakly positive antibody screen (indirect Coombs) from passive anti-D can be seen in the mother, and a weakly positive direct Coombs in the baby due to passive placental transfer of the IgG antibody.⁴

Since passive RhIG cannot be differentiated from mother's own active anti-D IgG in the case of prior Rh sensitization, a correct interpretation of a positive antibody screen in an Rh-negative woman requires the blood bank to have knowledge of prior RhIG administration, or more importantly absence thereof. This workflow is illustrated in Figure 2.

Management of the Rh-sensitized woman then escalates to the determination of paternal or fetal Rh(D) genotype. If the fetus is Rh(D) positive as determined by either cell-free fetal DNA in the mother or by paternal homozygosity for Rh(D), the pregnancy is monitored by following maternal anti-D titers and assessment of fetal anemia with serial Doppler Middle Cerebral Artery Peak Systolic Velocity (MCA-PSV) measurements and if necessary, fetal hemoglobin and hematocrit values via cordocentesis. In severe fetal anemia, intrauterine transfusion is indicated.⁵

Rh alloimmunization of the mother leads to Rh hemolytic disease of the newborn (Rh-HDN) in subsequent pregnancies with an Rh-positive fetus. Rh-HDN can manifest as a spectrum ranging from congenital anemia with reticulocytosis (Case 1) to immune hydrops (IH) due to hypoalbuminemia from excessive extramedullary hepatic hematopoiesis with even more immature and therefore nucleated RBC precursors (also known as normoblasts or erythroblasts) released into the circulation (so-called Erythroblastosis Fetalis ). The diagnosis of hydrops requires abnormal fluid accumulation in at least two of three fetal compartments (pericardial, peritoneal, and pleural) and generalized skin edema (anasarca). Thus, the infant in case 2 likely had evolving IH given the findings of hypoalbuminemia, ascites, edema, anemia, reticulocytosis, and an elevated nRBC count.

Although the fetal Rh(D) antigen leading to the formation of maternal anti-D is responsible for 50% of the cases of maternal alloimmunization and the most severe form of Rh-HDN, sensitization to the other antigens of the Rh locus (C, c, E, e) can also lead to Rh-HDN.^1,2

Besides intensive phototherapy and phenobarbital, which increases hepatic bilirubin uptake by ligandin and conjugation by Uridine Diphosphate-Glucuronosyl Transferase (UGT1A1),⁶ treatment of Rh-HDN with IVIG 0.5 to 1 g/kg over 2 h every 12 to 24 h may decrease the risk of needing an exchange transfusion.⁴

Conclusion

It is important for obstetrical providers and blood banks to inquire in Rh-negative women about both pre- and postnatal RhIG and in both past and current pregnancies to evaluate the risk for sensitization and hemolytic disease of the newborn. Extra vigilance is needed for recent immigrants with an absent, unverifiable, or unreliable history of prior RhIG administration. Timely communication between obstetricians, blood banks, and neonatologists in these situations is of paramount importance in optimizing neonatal outcomes in both current and future pregnancies. These two cases also illustrate opportunities for simple preventive measures. Automatic reflex to antibody titer (similar to RPR titer when a Treponemal antibody test is positive) and bypassing a separate physician order in pregnant women with anti-D could possibly have changed the course in case 1. A system for automatic blood bank notification of the obstetric provider of a positive antibody screen and automatic obstetric provider/labor and delivery notification of the neonatal/pediatric provider of a women in labor with a positive antibody screen would also likely have led to earlier detection and postnatal treatment in case 1.

In the newborn nursery, where a neonate may not be examined by a pediatrician until the next day, a protocol for early and frequent assessment for neonatal jaundice could easily be implemented for all infants born to mothers with a positive antibody screen.

In the case of the sensitized Rh-negative mother with an infant suffering from Rh-HDN, neonatologists can and must impress upon these parents the presumed recurrence of Rh-HDN in subsequent pregnancies and emphasize the critical importance of direct NICU admission for aggressive treatment with phototherapy, phenobarbital, and IVIG. For additional safety, any neonate born to an Rh-negative mother with a positive antibody screen, unless there is a clear history of timely prior RhIG, and any mother with identified anti-C, c, E or e-antibodies, must be presumed to be at risk for Rh-HDN and severe hyperbilirubinemia and should therefore be directly admitted to the NICU for serial TSB measurements and early treatment with phototherapy, phenobarbital and IVIG.

Footnotes

Acknowledgements

The authors would like to thank Ms. Minerva Vasquez, CLS, MT (ASCP), manager of laboratory services at Community Memorial Hospital for her help in obtaining additional information on the two patients described and help creating .

Ethical approval

This case series did not require ethical approval or Institutional Review Board review, as no human subjects were directly involved or could be identified. The pictures do not contain any patient-identifying information.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Bengt-Ola S Bengtsson

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