Anti-RH1 alloimmunization: At what maternal antibody threshold is there a risk of severe fetal anemia?

BACKGROUND: To define a threshold of maternal antibodies at risk of severe fetal anemia in patients followed for anti-RH1 alloimmunization (AI). STUDY, DESIGN, AND METHODS: We conducted a retrospective study of patients followed for anti-RH1 AI at the Lille University Hospital. The first group, severe anemia, included patients who received one or more in utero transfusions (IUT) or who were induced before 37 weeks of pregnancy for suspected severe fetal anemia. The second group, absence of severe anemia, corresponded to patients without intervention during pregnancy related to AI. Sensitivities, specificities, and positive and negative predictive values for screening for severe fetal anemia were calculated for the antibody thresholds of 3.5 and 5 IU/ml for the quantification. RESULTS: Between 2000 and 2018, 207 patients were included 135 in the severe anemia group and 72 in the no severe anemia group. No severe anemia was observed for an antibody titer below 16. For an antibody threshold of 3.5 IU/ml, the sensitivity was 98.2%, with 30.2% false positives. All severe anemias were detected in the second trimester; two cases of severe anemia were not detected in the third trimester. For an antibody threshold of 5 IU/ml, the sensitivity was lower at 95.6%, with five cases of severe anemia not detected. CONCLUSION: The antibody threshold of 3.5 IU/ml for the quantification and 16 for the titration allow targeting patients requiring close monitoring by an experienced team in case of anti-RH1 AI.

Risk factors for severe neonatal thrombocytopenia in cases of maternal immune thrombocytopenia.

AIM: Maternal immune thrombocytopenia (ITP) may induce neonatal thrombocytopenia (nTP), which carries a risk of neonatal haemorrhagic complications. Some risk factors for nTP have reached consensus such as maternal splenectomy and previous severe nTP, while others such as maternal platelet count have not. METHODS: We conducted a retrospective cohort study in a university hospital, including 145 neonates of mothers with ITP. We assessed the risk of severe nTP and bleeding complications. RESULTS: Severe nTP in the first 24 h after birth was more common in case of maternal splenectomy (OR = 4.4) and a previous severe nTP (OR = 46.9). Severe nTP at nadir (lowest platelet count during the initial postnatal days) was more frequent in cases of a previous neonate with severe nTP (OR = 42), maternal treatment during pregnancy (OR = 2.4) and a low maternal platelet count during pregnancy or at delivery. These risk factors were not significantly associated with an increased risk of neonatal haemorrhagic complications. CONCLUSION: In our population, we confirm the risk of severe nTP in case of maternal splenectomy or previous nTP. By monitoring the platelet count to its nadir, we identified three additional risk factors: maternal treatment during pregnancy and low maternal platelet count during pregnancy or low maternal platelet count at delivery.