Postnatal monitoring key in red cell alloimmunization cases

Postnatal monitoring key in red cell alloimmunization cases | Image Credit: © Bostan Natalia - © Bostan Natalia - stock.adobe.com.

Structured postnatal monitoring and timely follow-up are vital for managing neonatal outcomes in red cell alloimmunization cases, according to a recent study published in Pregnancy.¹

Pregnant patients may develop red blood cell (RBC) antibodies that differ from their own, increasing the risk of complications if the fetus inherits incompatible antigens. If maternal antibodies cross the placenta, fetal red blood cells may be targeted, leading to hemolytic disease of the fetus and newborn (HDFN).²

Peak systolic velocity in the middle cerebral artery (MCA PSV) monitoring is traditionally used to assess patients with clinically significant antibodies.¹ This method has a false positive rate of approximately 12%.

“Although MCA PSV Doppler surveillance is widely used in managing red cell alloimmunized pregnancies, limited data exist on neonatal outcomes when the threshold for intrauterine transfusion (MCA PSV ≥1.5 MoM) is not persistently reached,” wrote investigators.

Surveillance using MCA PSV doppler

The retrospective cohort study was conducted to evaluate outcomes in these pregnancies. Data between January 2018 and December 2023 were obtained from a single center of level 4 maternity and neonatal care units.

Pregnancies needing MCA PSV Doppler monitoring for red cell alloimmunization with an at-risk fetus or neonate not requiring intrauterine transfusion (IUT) were included in the analysis. Those with no antenatal or postnatal testing, needing IUT, or with multiple gestations were excluded.

Maternal and neonatal medical records were assessed for relevant data, including maternal demographics, obstetric history, red cell alloimmunization profiles, MCA PSV Doppler assessment characteristics, antenatal interventions, delivery characteristics, and neonatal outcomes. HDFN risk was determined based on antigen testing.

Antibody profiles and pregnancy characteristics

There were 40 pregnancies and 39 neonates with increased risk of HDFN included in the final analysis, 50% of whom had antenatal testing and 50% had neonatal testing. Anti-D was the most common antibody, observed in 52.5% of pregnancies. This was followed by anti-E in 17.5% and anti-c in 15%. Multiple antibodies were reported in 21.1% of cases.

Mothers were aged a median of 31 years and had a median gravidity of 3 and parity of 1. Red cell alloimmunization in previous pregnancy was identified in 60.6% of patients with documented alloimmunization history, but no prior IUT cases were found.

Neonatal intensive care unit (NICU) admission was necessary for 46.2% of neonates, while 56.4% required phototherapy to treat hyperbilirubinemia, 2.6% required transfusion, and 12.8% required intravenous immunoglobulin (IVIG). Only needing phototherapy was reported in 33.3% of neonates, and none received IVIG or transfusion as isolated therapy.

Anemia and hyperbilirubinemia treatment

RBC transfusions were given to 28.2% of neonates to treat anemia, with only 5.1% receiving RBC transfusions as isolated therapy. Postnatal therapy for hyperbilirubinemia was required for 61.5% of at-risk neonates, while 38.5% did not need treatment. Those not needing treatment were born to younger mothers vs those requiring treatment.

A reduction in birth weight was reported in the treatment group vs the no-treatment group, at 2859 vs 3420, respectively. NICU admission rates were 66.7% vs. 13.3%, respectively, and median NICU durations were 7 vs 0 days, respectively. However, gestational age at delivery did not differ between groups.

These results highlighted neonatal outcomes in red cell alloimmunized pregnancies without IUT monitored with MCA PSV Doppler. Investigators concluded there is a need for tailored prenatal counseling and structured postnatal monitoring.

“Future research should focus on risk stratification tools and standardized follow-up protocols to better identify and manage at-risk infants in this understudied population,” wrote investigators.

References

1. Arkerson BJ, Aghajani F, Modrall KE, et al. Neonatal outcomes among pregnancies with red cell alloimmunization requiring doppler monitoring without intrauterine transfusion: A retrospective cohort study. Pregnancy. 2025. doi:10.1002/pmf2.70090
2. HDFN hemolytic disease of the fetus and newborn. Fetal Health Foundation. Accessed August 29, 2025. https://www.fetalhealthfoundation.org/fetal-syndromes/hemolytic-disease-of-the-fetus-and-alloimmunization/.