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Neonatology

Poster Session 3

(770) Neonatal outcomes associated with clinically significant red blood cell antibody seroconversion in pregnancy

Wednesday, February 14, 2024
8:30 AM – 10:00 AM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Foundation Awardee
Objective: To determine neonatal outcomes associated with clinically significant red blood cell (RBC) antibody seroconversion in pregnancy.

Study Design: This is a retrospective cohort study of all pregnant patients who delivered at a multi-hospital system from 2016-2023. In this system, a type and screen (T&S) is obtained at entry to prenatal care, at time of admission for delivery, prior to administration of Rh(D) immune globulin (RhIG), or as clinically indicated. Patients with missing RBC antibody screen at delivery or no record of T&S at entry to prenatal care were excluded. All other patients with a positive screen at delivery were categorized as passively immunized due to RhIG, alloimmunized (antibody previously identified during the pregnancy), or seroconverted (antibody not previously identified in the pregnancy). Antibodies were described as clinically significant if associated with hemolytic disease of the fetus and newborn (HDFN) to any degree per ACOG Practice Bulletin 192. For neonates born to seroconverted patients with clinically significant antibodies, neonatal outcomes were chart abstracted. The highest total bilirubin was recorded prior to 96 hours of life as was phototherapy for hyperbilirubinemia, need for RBC transfusion, and neonatal intensive care unit (NICU) admission.

Results: There were 58,912 pregnant individuals with 71,384 eligible deliveries. 351 (0.5%) deliveries had clinically significant antibodies associated with HDFN, and among those, 168 (0.2%) seroconverted in pregnancy. Among those deliveries, there was one case of unexplained stillbirth at 29 weeks and another pregnancy loss at 19 weeks. Of the remaining 166 liveborn neonates, 78 had a total bilirubin level drawn (median 9.1, ranged from 1.1 to 30.1) and 22 required phototherapy. 27 neonates required NICU admission, 5 of which were primarily due to hemolytic disease (Table).

Conclusion:

Development of new clinically significant RBC antibody in pregnancy occurred at a rate of 0.2% with low incidence of associated neonatal morbidity. Routine third trimester assessment of maternal antibody status may not be indicated.