Background/Case Studies: Historically, Rh incompatibility was the leading cause of hemolytic disease of the fetus and newborn (HDFN). The American Academy of Pediatrics (AAP) guideline from 2004 strongly recommended for routine direct antiglobulin testing (DAT) on mature newborns ( >35 weeks) born to RhD-negative mothers to assess the risk of isoimmune hemolytic disease. However, the widespread administration of Rh immune globulin (RhIG) to prevent sensitization to D antigen in RhD-negative pregnant mothers has notably diminished the prevalence of Rh disease. As per the 2022 AAP guidelines, newborns testing positive on DAT can be managed as if DAT is negative if the mother solely tests positive for passive anti-D. This study examines the necessity of DAT in infants born to RhD-negative mothers.
Study
Design/Methods: We conducted a retrospective analysis examining data from mature newborns with Rh incompatibility at a community hospital from October 1, 2022, to March 31, 2024. Newborns whose mothers could make isohemagglutinins against the infants’ red cells were excluded from the study. Variables such as maternal antibody screen results before delivery, fetal DAT results, and phototherapy administration were analyzed. Knowledge of RhIG administration date was obtained per SOP. Fisher’s exact test was used for statistical analysis, with p > 0.05 indicating significance.
Results/Findings: Over 18 months, 294 newborns with Rh incompatibility were identified based on the inclusion and exclusion criteria. All mothers of these infants tested negative on prenatal antibody screens and received RhIG at 28 weeks of pregnancy. One mother became sensitized to the D antigen and developed true anti-D (0.3%). Although her antibody screen was negative 16 days before delivery, it turned positive with a titer of 256 just before delivery. The newborn tested positive on DAT, necessitated phototherapy for hyperbilirubinemia, and was discharged in stable condition. Among the remaining 293 mothers, 189 tested positive for passive anti-D (64.5%), while 104 tested negative. No other alloantibodies were detected. Out of the 189 mothers, 31 newborns tested positive on DAT (16.4%), whereas out of the 104 mothers testing negative for anti-D, 6 newborns tested positive on DAT (5.77%, p = 0.01). Only 2 infants with hyperbilirubinemia necessitating phototherapy were identified, both testing negative on DAT. Conclusions: Our findings suggest that routine DAT testing in newborns born to RhD-negative mothers who do not develop alloantibodies during pregnancy is unnecessary. The majority of RhD-negative mothers receiving RhIG at 28 weeks exhibited positive antibody screens just before delivery. If positivity is solely attributed to passive anti-D, there exists no associated risk of hemolysis or hyperbilirubinemia in the infants, irrespective of DAT results.
